the AI is limited yes, but simply coding (NOT required) there is NO limits
there is doors, what you can lockup, and unlock in the game with key.
not MASSIVE level, but a nice size, but if you dont get in the map EVERY single entity, you can make quate big level
there is NO inventory, exept the weapons, AND if you learn to script, everything is bossiple!
you can tell whatewer you want in the game, like videos, pictures, etc.
There would be REALLY good graphics, and just make the map, and show to the freands of yours, and they keep wonderin "DID YOU DID THIS!?"
and YES, ofcourse u can put your musics in the game!!
hope this helped you a little.
PS: BYE THE FPS-C, i´m sure, that you dont repent!!