Cell didn't really place those rules for his advantage, though. He just thought it would make for more interesting sport.
still hes a villain any smart hero (which goku isn't which is why I ultimately do say fuck it, it is what it is) would think something was up. not the mention the fate of the world is at stake and your going to play a game to decide it? and try to play fairly? sorry when someone threatens the world you don't play fair, you play to win.
Given that the world was essentially hostage, they kinda *had* to play by his rules. Keep in mind that Frieza blew up Namek as a last-ditch effort to kill Goku and Cell *could* have done the same even if he ultimately lost. Also remember that Cell could likely have survived in space -- since he'd need *some* way to leave the planet -- so he could have just flown up and destroyed everything. ---