Here's an idea for a core theme:
Reprint old characters from each franchise.
Example - for SF, reprint one character card from each of the the original eight World Warriors (any version would be fine, like Ryu9, Ken4, Guile3 ,etc). Print about eight or so characters from each license, and make them prize support in some way; participation promos, whatever. Then you get the old nostalgia and awesome win-ness, plus new combos and stuff, and increasing the character pool.
If you want a real core SET, then do that, but reprint ~3 support cards from any given set for each character. This creates a 32-card mini-set of solid cards. I like something that Fred said - do you know how badly I'd love to see Solid Punch reprinted? Or ffs, VAST RESOURCES? Ninjutsu? Misdirection?
