what i understand from the information that you give, is that you want to make a manga with alot of diff world and drawing style, that give people like seeing alot of diff manga in 1 manga.
and alot of well know char in those world , in another world like kingdom heart in a way.
i don't think the idea is a problem here, i think the real problem will be you, as in your writing skill is.... well let put it as not good for making a manga.
and you will not be able to get so many good artist to work for you unless you pay. if is no pay, only low lever artist will come and help you and i am sure that will be very bad..... many weird drawing will come out......
so if you really want to make this manga you will really have to think, what price you willing to pay , how much money and how much time. if your plan is just no money and very little time then i will say it can't be done.
if is $0 and alot of time, then i will say you need to improve your way of writing, try to make it easy for other to understand your story, then maybe some good artist will help you base on a good writing skill and story.
if is alot of money well, just hire some 1 to help you to make.