I would personally avoid adding ships that aren't referenced as being there in any other sources.

http://starwars.wikia.com/wiki/Battle_of_endor

On the sidebar, there's a section labeled "Strength", which lists all the ships and such present in the battle as portrayed in the movie and EU. I don't propose showing every single one of these ships, or even that any of them absolutely must be shown at all, but if any additional ship classes are to be added, I think it should use that as a guideline. So I'd avoid the N-1s and ARC-170s, as they've yet to show up there officially and there's already plenty of ships to choose from that were there.

I would love to see more ship classes, as long as it builds upon what's already established.