ROM Hack Phantasy Star Zero Possible Rom Hack?

[Windancer]

Probably a Really stupid question. Would it be possible to Hack the Phantasy Star Zero Rom to make Eternal Tower playable online. It takes 4 hours to run through which ive done 3 times but would be much more fun to runthrough online with some friends. It's only available in offline mode and opens up as an extra stage after you beat the game offline