NBA 2K13 Cheats
Hmm no, this ain't possible.
I know you can use cheatengine to increase the height of your player when you are creating him so that can give you a big advantage. I am currently testing my center with heights of 7'3, 7'4, 7'6, 7'8 and 7'10 when you are 7'4. Being taller then 7'8 is really overkill though, because at 7'8 you can block shots like a beast.
But to answer your question signature skills you can only change after your rookie showcase. Stats however you can change just use a cheatengine table its posted in another topic here.
[Edited by Apocalypse11, 7/3/2013 3:32:03 AM]