Hasbro over the years has developed a large number of toy franchises, including the popular G.I. Joe and Transformers, to more obscure ones like M.A.S.K. and Inhumanoids. Over time they have also bought out other toy companies like Coleco and Kenner, as well as the gaming company Wizards of the Coast, which previously bought TSR. This leaves a large number of franchises in a wide variety of genres under one roof. They breakdown as follows.
Characters originally created by Habsro
G.I. Joe
Transformers
Visionaries
Battle Beasts
C.O.P.S.
Inhumanoids
Air Raiders
Action Man
Medabots
Xevoz
Robotix
Coleco toy company
Sectaurs
Starcom
Galoob toy company
DragonFlyz
Golden Girl
Zbots
Tonka toy company
Go-bots (and the Rock Lords spin off)
Supernaturals
Spiral Zone
Kenner toy company
M.A.S.K.
Bone Age
Shadow Strikers
Milton Bradley game company
Heroscape (Game/miniatures)
Wizards of the Coast gaming company (Which owns TSR)
Magic The Gathering
Dungeons and Dragons
Alternity (Science Fiction Role Playing Game)
Netrunner
Hetacomb
Dreamblade (Minatures)
Ars Magica? (RPG)
Everway (RPG)
As you see, that is a wide variety of genres, from fantasy, to science fiction, to military action, and even some horror. Lots of potential crossover there.
Transformers
G.I. Joe
He-man
Star Wars
Inhumanoids
Air Raiders
Chuck Norris and His Karate Commandos
Silverhawks
Thundercats
Visionaries
Defenders of the Earth (A King Features cartoon featuring The Phantom, Flash Gordon, and Mandrake the Magician, who together fought the forces of Ming the Merciless, Flash Gordan's arch enemy.)
Also in the early 80s they published original stories about Indiana Jones. That series ended in 1986, but they still had the rights in 1989 as they adapted The Last Crusade.
Now I'll guess that they would not have allowed to crossover with Star Wars. Still had the owners of the other properties allowed, there could have been a huge crossover with all of the above characters, and the Marvel Universe. Pretty much all the big 80s franchises are listed above. It could have been the crossover of the decade. For the record, Transformers did cross with Spiderman, as well as G.I. Joe. So potentially more could have happened.
Finally if DC possibly could have been thrown into the mix, they could have thrown in their own characters. They also published in the late 80s, M.A.S.K. Spiral Zone, C.O.P.S. Centurions, and Doc Savage. The Shadow was also passed back and forth between Marvel and DC at the time. So if all the legal wrangling could have been pulled off, the two companies could have published a giant crossover.