This plane would have a fuselage based on the F100 cross section, also using it's nose/cockpit, T-tail and some of it's systems. Obviously there would need to be a newly designed high wing mid section (or low wing engine top mounted) with a new CFRP wing. In this configuration I could image an FP80, FP100 and FP130. Engines could range from the AE2100, the PW100, GE38 and TP400-D6.
I know it's just silly speculation, but obviously I don't mind that. Any opinions on this?
Below is a very rough example of what the FP80, FP100 and FP130 may look like:

I'm not in anyway affiliated to Lila Design, just used a graphic from an airliners.net thread (hope that is okay).