If you're looking for an assault ship, the Neb-B frigate would seem to make sense. They are bigger than Vettes, are well known for adaptability (being hospital or war ships), and are in ROTJ, making them recognisable.

Failing that, I'd go with a dreadnought or assault frigate.

It's meant to be an Old Republic warship used before Star Destroyers and the like, it's purely EU though, so you won't be finding them in the prequel movies or anything. I think the first time I saw them was in the old West End Games Star Wars Roleplaying Game, they also get a lot of action in a lot of the novels. They tend to get used by all factions Rebels, Imperials and everything inbetween when you want a medium sized capital ship. I've posted a link the the SW.com Database below.

http://www.starwars.com/databank/starsh … index.html

Talon1579, I see where you're coming from when you suggest a Nebulon-B Frigate as the assault ship, but the problem with that is we need something small enough to land on the SSD/Star Destroyer so it can off load it's cargo of vehicles, troops and equipment. Which is why I suggested a Corvette as that is large enough to carry that sort of equipment, and small enough to land in an SSD's hanger bay. Alternatively if we go with the standard size Star Destroyer the smaller hangers would require a number of the Imperial AT-AT carrying Dropships, or maybe Gallofree Transports would be the Rebel equivalent.

A Neb-B might make a good launch platform for the the Rebel fighters for the space map, and could perhaps provide cover for whatever style of assault transports the Rebels choose to invade the Imperial ship with.