Bioware style RPG set after SG1, players can be a human soldier, a free Jaffa, or a minor Goa'uld on the run from justice with the option to assemble parties of races and roles from throughout the show. Each race would have certain unique abilities- humans would have the most equipment options, Jaffa would have superior strength and health regeneration, and Goa'uld would be able to use unique gear unavailable to other races.
All alignments and paths would be open to all characters, so if your deposed system lord feels bad about centuries of dictatorship, you can team up with those you once enslaved to fight for freedom, while an SG trooper could hole up in some remote world and go all Colonel Kurtz if that's what you want. Enemies would include extraterrestrial criminals, Goa'uld nobles, Wraiths, and other baddies from the show, with perhaps some new ones thrown in as well.