its going to be difficult to make a decent hack with no entrance or exit editing or zone editing, also not to be a party pooper but imho declaring your making a fully fledged rom hack should really wait until you have a good chunk of it done you see too many "IM MAKING A NSMB2 HACKK!!!!" threads that never amount to more than a video or a handful of levels before they loose interest......why not all the people wanting to make a hack team up, focus on 1 world each and make a nsmb GBAT (gbatemp) edition, it would be more likely to get finished
I've never seen anyone saying they are making a NSMB2 level hack, besides me and that one guy from almost a year ago who disappeared from the internet.