A while back I got turned on to sforz's mods and I especially love Destinations. It's simple, unobtrusive, and complements simple carriage expansion mods well by adding carriage stops that allow for travel between smaller settlements that don't have carriages like the major cities.

The downside to me is that there are a few mod-added/enhanced places or inconvenient spots to reach that it would be nice to get to without having to haul across all of Tamriel on foot every time when you play without fast travel - places like Granite Hill, Stonehills, Darkwater Crossing, and Fort Dawnguard. So I added carriage stops to each of these 4 places, and linked them to the existing network. See the images for a map of all stops - orange dots and lines are the original network, blue dots and lines are my added stops and connections.

New connections:

Whiterun <-> Granite Hill
Falkreath <-> Granite Hill
Rorikstead <-> Granite Hill
Rorikstead <-> Stonehills
Morthal <-> Stonehills
Dawnstar <-> Stonehills
Kynesgrove <-> Darkwater Crossing
Riften <-> Darkwater Crossing
Ivarstead <-> Darkwater Crossing
Mixwater Mill <-> Darkwater Crossing

Riften <-> Fort Dawnguard*

The trip from Riften to Fort Dawnguard is quest aware. In order to travel to Fort Dawnguard from Riften, you must have started and/or completed Awakening. If you arrive at Fort Dawnguard on foot, you can use the carriage stop to travel back to Riften regardless of quest status. 

• It is feasible that this quest requirement might conflict with mods that change how Dawnguard starts. At Your Own Pace - Dawnguard is compatible, you will be able to use the carriage to travel to Fort Dawnguard after freeing Serana. Let me know if you experience issues with the fort travel option enabling once you have begun the Dawnguard questline and I can see if there are relevant conflicts.
  

• When traveling from Riften to Fort Dawnguard, the carriage stop is at the crossroads a little ways down from the fort and you'll have to walk up. It's significantly shorter than having to hike all the way from Riften to Dayspring Pass and up like normal, but this was the best compromise to prevent issues with the DG questline and any ambushes that occur. Again, it's feasible that mods that edit the DG questline or any of the ambushes may see a little weirdness. Let me know if you experience issues and I can check. Mods that edit the Fort Dawnguard area should mostly be compatible as I tried to place the bench out of the way.
  

These carriage stops were placed based on common mod-added towns and locations and intended to be out of the way of added items but still accessible. Clipping should be minimal but it's possible that certain town mods/overhauls will cause clipping. Granite Hill in particular is tricky since everyone has a slightly different approach to the town. I picked a spot along the road which should be mostly out of the way, but let me know if you see significant clipping or access issues with a specific version - if you ask nicely I may patch it.

• A patch is provided for Schlitzohr's Granite Hill Village to move the carriage stop out of an added wall.
• Northern Roads possibly needs a patch for the various Granite Hill mods - let me know if it does and I will take a look. Stonehills and Darkwater Crossing shouldn't require much patching attention, but let me know. I can't check every combination myself.
  

Let New Destinations overwrite the scripts in Destinations (theirs are in a BSA, mine are loose so this should not be an issue) as the new stops are enabled by some script edits.

Please don't ask me to add new stops I made this over a year ago and have since forgotten what the hell I'm doing lol.

All credit to sforzinda for creating Destinations and all their great mods.
Credit to gamebanshee for the map resource they used/I edited