While I do miss the jump height, adding in acrobatics would be entirely meaningless.
I like the "second story thief" concept. The rooftop to rooftop traveler. The thing is, none of this is useful in Skyrim. Too few buildings, if any have meaningful second story access (maybe the village general store) to justify an acrobatics or even a climbing skill.
I agree that the game isn't designed with it in mind, and because of it there wouldn't be as many uses, and that's a shame. It doesn't mean it would be entirely meaningless, though. Morrowind didn't exactly design the world around acrobatics. Some few areas were, and some were designed around levitation, but by and large the world was as accessable to someone with 5 acrobatics and no magic as it was to a vampire with 150 acrobatics and a levitation power.
Without the terrain or design acrobatics simply becomes a useless skill players would accidentally level from. With the current leveling system this could hurt players due to scaling.
I've made two posts in this thread earlier proposing how to remedy that problem, wherein the first perk in the tree would provide a small bonus (5% faster run speed, for example) and also allow jumping and sprinting to give XP towards athletics (to be merged with acrobatics). Without the perk, no XP is gained, and thus no accidental leveling. Would this system be ok, in your opinion?
Also, each major skill group has 6 skills each. Adding in Acrobatics forces the need for two new skills to maintain symmetry among the major skill types. Athletics was mentioned, but once again, its difficult to define a skill tree around just going faster. Also, once again, accidental leveling.
Why do they need to maintain symmetry? There's no reason whatsoever for the 3 skill categories to have the same number of skills associated with them, but for the sake of argument: Athletics could be merged with acrobatics and hand-to-hand could be added into that, as well, making the tree much more than just "going faster". For the combat and magic skill trees, you could have spear and - as you suggested - mysticism.
As long as rolling is never put into combat.. rolling in combat is stupid. A better option would simply be an ability to cause a side/back/forward-step by jumping in a direction while in combat; whereby you take a step around the opponent, or 'lunge' forward/backwards rather than jumping. These are basic skills in pretty much all combat arts and is much more useful that rolling. It'd also give you situational defence against both horizontal and vertical attacks.
I support this. I'd like to see Oblivion's dodge make a return, but with a different animation. They've done it before, why not again?