I think its more update than sequel. It have new graphics, more hills, more terrains to fly and bit changed cockpit to more match F-117. All other is pretty same. Personally I like F-117 more. Full VGA palette is great enhancement.

That 'Theoretical mode' just add onboard gun and two extra weapon bays as was in original F-19. BTW Testor 1/48 kit of F-19 (Company that developed fictional F-19 design) had two bays as F-117 and no gun.

http://www.fantastic-plastic.com/TESTORS%20F-19%20STEALTH%20PAGE.htm

F-117 is actually something like Gold Edition of F-19. So I really see no reason not to add F-19 to this pack. To me F-19 has special charm :)