This mod allows you to swap to directly controlling any member of your clan through the clan menu.  You can also make them the party leader, or even replace your character as clan leader.

Note that you can't switch during a battle- it has to be from the clan menu (Press L).  This is great for helping a clan member to level a skill, or for using a clan member with better combat skills in battle.  This opens up a lot of options; for example, you can have a companion built and kitted out for siege battles, and another optimized for field battles.  You can even switch to clan members controlling other parties out in the world.  Also, while controlling a clan member you can modify their appearance, so that's nice (though other mods allow that now anyway).

If you are looking for a smooth and balanced experience, I recommend only switching to characters within your party.  Also, I recommend that
whenever you switch to a character, you also make that character Clan Leader and Party Leader as well.  For short-term swaps, however, you probably don't need to bother.  At this point, you should be able to ignore this advice without any game-breaking bugs, but you may encounter weirdness, soft-locks, or crashes.  See the known bugs section.

Update 1.2 (4/26):
-Changed money transfer mechanic to avoid money loss or duplication, and random filthy-rich party members

• It looks like everything works intuitively, but please report any odd behavior if it happens.
  

-"Swap Character" now closes the menu.  This will prevent a known bug that was causing crashes when the player switched characters more than once without closing the menu.
-Relations with notables are now transferred between characters when they become clan leader.

• Previously, if you had switched a character to clan leader you'd be back to square one with regard to relationships in villages and towns.  That shouldn't happen anymore.
  

Update 1.1 (4/16):
-Two new buttons have been added: Make Clan Leader, and Make Party Leader.  Now you can effectively switch your main character completely.

• "Make Party Leader" is useful if the character has a skill you need at that moment (Roguery stands out, since you can't even assign it as a clan role), or if you want to level a companion's skill that only goes up if they are party leader (Trade, Roguery, Tactics, Leadership, Steward... etc).  But switching your party leader to somebody who isn't the clan leader means you might forfeit some major party size bonuses.  So if you switch a party member to the leader for more than a second you should probably make them the clan leader as well.  Keep a close eye out for this-- you don't want to lose soldiers because your party limit went down.
• At this time, it is probably best if you generally make sure that whichever character you want to control is the party leader and clan leader.  Having your clan leader, party leader and main character as three separate people does work, but it can lead to some oddities with finance.  It's good for a temporary switch while training, but party wage expenses/surpluses will be passed around between characters in unpredictable ways.  The game expects the main character to always be clan and party leader.
  

-You no longer need to deal with characters having separate finances.  Each party now effectively shares a single pool of gold.  Why not one gold total for all parties?  See "How Money Totals Work" further down the page.

• Be aware that if you are upgrading from mod version 1.0, your characters' gold totals will be set to whatever the total of the party leader (probably your starting character) is when you switch to them.  If one of your companions is holding all of your money, you're going to lose it.  I recommend using the "Character Export Import" mod to transfer gold, if this is a problem for you.
  

Update 1.0 (4/14):
-Updated to use the Harmony patch system

• Previously this mod used bad modding practices that made it prone to breaking and other issues.  It also made it incompatible with Vortex.  I have finally managed to figure out how to get the mod working with Harmony patches, which is much better practice and fixes many issues.
  

-Added console command to switch to any character on the map for users of Developer Console mod (campaign.bodyswap_to_hero)
-Fixed some bugs (see below)

Fixed Bugs:
The following bugs appear to be fixed from my limited testing.  But you probably ought to be aware of them in case they pop back up.

• Swapping characters will move all active quests to "Past Quests".  This will break the main quest.
  

• Crashes can occur.  This appears to be connected with doing a quest that tracks items or party members (Deliver Herd, for example).  More testing needed to confirm.
• Characters' money totals are kept separate.  See explanation below for details on the fix.
• Swapping to a character and then swapping to another character without closing the clan menu in between will often cause crashes the next time
  you enter a settlement.
• Relations between notables and characters are handled per clan member.  If you switch to another character, you may find that your relations are
  reset until your switch back to the character that has a relationships with notables.

Known Bugs:

• Doing something that triggers a conversation with the companion you are controlling will lock you in a conversation with yourself.  You'll have to alt+f4 to get out of it.  If this becomes a problem, try the "ChilledCompanions" mod.
• Behavior surrounding characters who are not part of a regular old party on the map can be very buggy.  Bugs have been reported stemming from switching to characters involved in sieges, characters governing, staying in, or being children in cities or castles.  If the character isn't in your party or in another party moving around the map, make sure you save before you try switching to them.  In fact, it wouldn't hurt to save before switching to anybody.
• Budgets and finance can get weird when controlling a character who is not clan leader or party leader.  The tooltip for daily income doesn't always reflect your controlled character's finances.  While the mod's logic for handling money has helped avoid odd or inconvenient behavior, there is still the possibility or spontaneously creating or destroying money.  The best way to avoid odd behavior is to always make the active character clan and party leader as well.
  

I suspect there will be more bugs cropping up.  The game makes some assumptions I basically cut out the game logic that cancelled quests when the player switches characters.  In vanilla, the player only switches characters when their character dies.  I wouldn't be shocked if this created bugs, especially if the player character were to die.  However, that isn't necessarily true.  But if something strange like that does happens you probably know who to blame.

Installing the Mod:
Previously this mod was not compatible with Vortex.  It is now.  So just click the button.

Using the Mod:
1. Press L to enter the clan management screen
2. Select a character.
3. At the bottom of the screen is a "Swap To Character" button.  There isn't any real feedback until you close the clan menu, but you'll see you are now controlling the selected character.

If you use the developer console mod and want to switch to literally anybody on the map (again, I'm only one person and testing is limited... expect bugs) you can now access the body swapping function with campaign.bodyswap_to_hero.  This will bypass the money handling system described in the next section.

How Money Totals Work:
Originally, I had hoped to make all of your characters use the same gold total as your main character.  However, this is not a good idea as long as you are able to switch to companions leading different parties.  Parties and caravans seem to use their leader's wealth to determine if they pay you, or if they can recruit, or buy, etc.  If your main character's gold total transferred over, that could easily break a lot of things.  On the other hand, if you have a few companions in your party that you like switch to, it will become very irritating for those characters to keep a totally separate gold total, especially since there is no way to transfer money directly to and from clan members. 

Therefore, I have made the mod set the character's gold total to the gold total of their party leader at the time the swap occurs.  When you make a character the party leader, their gold will be set to the gold total of the previous leader.  Effectively, the party will share a single pool of gold.  I think this is the best of both worlds, but the behavior of clan party gold totals isn't totally understood by me at this time.  This could cause imbalances (for example, starting a caravan with a member in your party who you switched to when you were rich-- will they keep that gold total? Will it affect the payout of the caravan?).  I don't know, but if you care to test I'd appreciate if you post any information.  If you are worried about breaking the balance of your game, you probably shouldn't be switching to caravans and stuff anyway.

Final note:
I have no intent to support this mod in any way.  I might, but I might not even answer questions.  I've been shocked at how much I have been supporting it, but I wouldn't count on that in the future.  If it breaks, I'll fix it if I'm still using it myself and feel like doing it.  Now that it's a patch, that's a lot less likely.

On the other hand, feel free to do what you want with the mod as long as you lie and say you did it all yourself.  Re-upload, sell it as DLC, whatever.  Anything goes!  If you make a version with more polish or meaningful feature additions I'd be happy to link to it from here.