Combine Lockpicking/Pickpocketing into Larceny, bring back an Acrobatics/Athletics type tree that lets me climb sheer surfaces and jump on water and other crazy stuff like that.
I don't know if I would be pro Acrobatics/Athletics making a return unless there was some really compelling perks to go along with them and an interesting way to improve them. Personally I hated having to jump all over the place to up my Acrobatics in Oblivion. Honestly, how often was it really necessary to jump in that game? I would basically be running across a field and decide "hey, I need to be upping my acro skill, let me jump run and level this up, derp".
EDIT: Forgot why I was originally posting. I liked the increase in rare loot and gold of the lockpicking tree but it was ridiculous that you could get the "easier master locks" and "picks no longer break". Shouldn't perks in a perk tree complement each other rather than compete. There is literally no reason whatsoever to get both perks.
Also, I loved the lockpicking minigame. However it might be more fun if there were different kinds of locks or other distractions to picking them similar to Bioshock and it's various lock traps.