Zahid Shabir :
what about having a CD version and the steam version
If you buy two separate copies, then maybe. As long as the CD version isn't registered a Steam game.
*Don't quote me on that though, because I'm not sure about the GAME SAVES. Both versions may try to use the same folder in "Documents".
I don't understand why you don't just try your mods then if that doesn't pan out to reinstall the game (make a Steam BACKUP so you don't have to download it again).
If somehow you were BANNED what does that mean?
Worst-case is you have to buy another copy of the game in which case you are NO WORSE OFF than you would be by getting TWO versions right away.
BANNED probably means your account though, so you can probably make another ROCKSTAR account.
*And it's MULTIPLAYER only. You can mod single player without reprisal.