There is an easy convenience improvement, a so called “low hanging fruit”.
-> When you auto travel, and are overloaded, you shouldn’t manually need to put stuff on your horse and then put it back. The game could just check if your overload fits on the horse, and calculate that buffer into the check for auto travel max-load.
Should be one little change in the line of code checking the stat 
Is that from your years of game coding? what may be “simple” to you could a coding headache.
Anything is possible. It goes without saying, that this is a vast generalization, that nevertheless has a high probability to be true. Game logic is sorted in game objects, and if its C++ they can access each other with dereferencing the objects in the classes. It is probably not much work, if the code is clean and thought through.
And how exactly would that enhance the game? Managing storage is already made far too easy, so at least this adds a little bit of grit. It takes two seconds to transfer your loot to the horse. Besides, this whole thing becomes irrelevant when you play in hardcore mode since there is no fast travel.
How exaclty does “shift A to B”, travel, “Shit B back to A” enhance the game? That’s not “managing” anything, instead that’s no-brainer GUI work. To “manage” something, you need a challenge and contradicting goals and requirements to fullfil. This is not “manage” this is “labour”.
Examples of manage mechanics:
-Food vs Weight
-Sleep vs. Time-Critical events vs. Distance to bed
-Protection vs Noise level vs Carry load
etc.
And in a real based medieval world which is based on real medieval, you have to do it by yourself.
And what you decribe are systems to simulate reality things. Your capacity problem is only an improvement to made one thing faster and easier from handling.
As for storage management, consider this: some perks make food in your inventory spoil slower, so you might want to carry those on your person, while metal loot can easily go on the horse. And there are potions you might want to keep on you as well so you can use them during battle when your horse is not accessible. The fact that you need to manage your storage usage yourself adds realism. Want to use a Lazarus potion during battle? Drat! You left them all in your saddle bag! Better prepare for battle properly next time.
Reality as in “I teleport my stuff to my horse while in the basement stealing stuff?”
Or reality as in “I ask Scotty to beam my horse from the town 5km to my spot in the woods?”
Need I go on?
So wouldn’t “auto load horse when travel” simply be a convenience handling improvement, like you say? Auto-travel is a comfort feature. Improving handling would only fit the purpose of the feature.
