I cannot give either of you XP.
As far as the big Charisma, wouldn't the jangling of it hinder my tumble and cause nutcracker damage in Peasants and Plagues?
As far as the feats, you are right. However, I just don't find a +2 to be worthy of a feat. I relooked at feats though and found Daredevil Athlete that would give +5 3x per day. Better, but still not worth it.
As far as magic items, I know in theory you cna make one, but it would be a much easier sell to a DM if I could point at an existing item that boosts Tumble...
Another idea - any way to take 10 or 20 on Tumble while under stress?