This mod reduces spell cost when not wearing armor.

New version 2.0!

Requires SKSE (not just for SkyUI: it uses some of the SKSE Math functions)
Requires SkyUI in order to access the MCM

The unhindered Magic effect can now be configured using an MCM, with two different modes:
Using the Fixed mode gives the same effect as in version 1.0.
Using Dynamic mode gives an increasing effect based on the highest spell school mastery attained.

The new Dynamic mode is a new way to experience Unhindered Magic! Instead of a flat 5% cost decrease for each body part not covered with armor, the percent decrease depends on your highest spell mastery level in ANY of the spell schools. So, If you are a Novice in any spell school, you get a 1% cost decrease for all spells in all schools. If you are an Apprentice in a school, you will get a 2% decrease. This scales up to the previous 5% decrease when you are a Master in any school. When you have yet to unlock any of the mastery perks, you will not receive a bonus when not wearing armor.

I made this mode because it seemed to me that an inexperienced magic user really wouldn't benefit as much from being unencumbered as an experienced mage. Thus, in my opinion, Dynamic mode is more immersion friendly. However, if you liked the previous fixed cost reduction, the option is present in the MCM.

In addition, I've added a new feature where all spells in a school gain a fixed percent cost decrease whenever you gain one of the mastery perks in that school. By default, this feature is turned off (set to 0% per perk) but can be configured in 1% increments up to 6% per mastery perk. Thus, a Master in Destruction magic can gain up to 30% cost reduction for all Destruction spells, in addition to the original Unhindered Magic effect, the normal half-cost spell benefit that comes directly from the perk, and any cost reductions from enchantments.

The MCM also has a slider allowing you to determine how often the maintenance script runs. The script is designed to be low impact, and normally only looks for changes in mastery levels when run. When a change is detected, the script updates the cost decreases accordingly. I've carefully designed the script to limit any script lag to a minimum, and in fact no lag should be noticeable under normal operation unless there is a high script load from other mods. By default the script runs every 10 seconds, but this can be changed to suit your needs.

Please let me know how you like the new version! Give any feedback or feature suggestions, and I'll see about incorporating them into future versions. And, of course, let me know if there are any bugs so I can remedy them.

Installing the new version:

You do not need to remove the previous version first. Simply update the mod and you should be good to go. Note that the MCM has a button which allows you to disable the cost reductions for your convenience in the event you wish to uninstall the mod.

Details:

Spell cost is reduced by 5% for each armor piece not worn. So, for example, if you are wearing Boots and a Cuirass, but not Gauntlets or a Helmet, you will cast spells for 10% less mana. You will receive the full effect when wearing clothing that is not considered armor (or no clothing at all).

This mod is inspired by a similar effect from Balanced Magic by Mysty (http://www.nexusmods.com/skyrim/mods/2275/?). I liked the idea of this effect, but did not want all of the other changes from that mod, and so was inspired to try and create the effect for myself. The contents of this mod are the result, and are entirely my own original work.

This mod is designed to complement Simple Magic Rebalance by Gruftlord (http://www.nexusmods.com/skyrim/mods/45021/?). I think that Gruftlord's mod is a great balance change and generally beneficial to magic users, but it does make it hard to cast high level spells without an immense mana pool. Hopefully, my mod makes things a little bit easier.

I made exceptions for the Diadem of the Savant, the Mask of Clavicus Vile, and the Dragon Priest Masks so that the 5% spell cost reduction still applies when any of these are worn. These all seemed like reasonable exceptions because they are all unique magical artifacts, and many of them are geared towards mages. However, any mod that changes these items may cause them to prevent the 5% cost reduction for helmets when worn.

Compatibility:

Two versions exist: One for Vanilla, and another for Dragonborn.

This mod should be compatible with virtually anything. It does not alter any Vanilla perks, spells, or magic effects. It does add a new keyword to the Diadem of the Savant, the Mask of Clavicus Vile, and the Dragon Priest Masks so that they do not prevent the magic cost reduction. Besides this, however, no Vanilla forms are changed.

I am not entirely certain if there is any detrimental effect to removing this mod mid-playthrough. However, a simple uninstallation procedure is to open the console, type 'help unhindered' scroll up (using Page Up) until you find a perk named Unhindered Magic, and type 'player.removeperk <########>' where the #'s are replaced with the value corresponding to the perk.