I'd utilize Explorer's Edition, although edges, flaws and powers from later editions can be added.
- Shaken can only be immediately recovered from on a raise; a simple success still leaves you out of action for the
- Leadership edges only affect extras, not Wild Cards such as other PCs
- Different incapacitation table
- Different skill list, although skill lists need to be tailored to the setting anyway
Proposed settings that stick very close to the basic rules, so can be grokked without too much reading:
Degenesis Rough: Conversion of the post-apocalyptic RPG of the same name.
Midgard 1880: Generic action-adventure in the late 19th century. Can be played by SW rules as is, with adventures reaching from Indy Jones dungeon-crawls over murder mysteries to gothic horror.
Pirates of the Spanish Main: Swashbuckling in a 17th century Caribbean that never was, based on the WizKids table-top of the same name.
Zombie Run: Zombie survival à Romero
