For BOF3 Teepo works better in solo party. Or just 3 teepos. He is not reason of crashes. There many party combination, that breaks game. Also yeah, story event often freeze game on talks, when you have hacked chars. But thats hardly unique caseXD. Even Seph in FF7 do that, until you mod him instead of hacking. There is some sprite editor, but it cant open .eml files from both psp & ps1 versions, so I have no idea, how to use it.
As for Vita hacking, there is Rin cheat plugin for save editing (but its old & mostly useless) & gohanmem tool from chinese developers. That tool is awesome & thats is what I currently use. It can create codes, scan memory & even directly edit games memory on the fly, which I consider best method. Cold steel is not that easy to hack, cause party address changes IN EVERY ROOM, AFTER EVERY LOADING SCREEN (yeah, curse falcom, but they did their job this time).
But if you truly need it, PM me & I explain you what I currently know