Akunin said:
I rember with fondness the 1e Thief-Acrobat, and liked the 2e version, as well. The 3e T-A is pretty boring in comparison (although Fight Anywhere and Cartwheel Charge are fun abilities).
You could replace the defensive fighting, kip up, fast climb and move anywhere abilities with straight Acrobatics bonuses to Climb, Jump, Tumble and Balance skills, like in the OA blade dancer and ninja spy. I would give a +10 bonus at 5th level, and a +20 bonus at 10th level. This would also let the thief-acrobat automatically take 10 on any of these skill checks, which makes sense for someone who devotes their training to acrobatics.