Just saw my name up here - sounds like a great idea, and I hope it will be able to work. I've seen some that seem to.
As for the cultures... Honestly, my thought is to keep the cultures as they are (if possible, although cards that need errata anyway could have their culture re-examined) and have the cultures gain support through Development's sets when we're ready to do that.
That said, I personally have Lackey and GCCG, but no other program. Obviously, Lackey would be incredibly easy to modify - it's designed to do so, after all. GCCG, on the other hand, in any case would need us to know who uses the Virtual Cards and who doesn't - in order to play with the people that don't fairly.
What I'd do, at least if/until an official update is put into it, is have two folders for images - one with the virtual cards and one with the original version of those cards. The player would simply have to replace when they switch to playing with/without virtual cards.
Personally, my goal would be to remove the X-list for every format. I'm not including the set-wide bans, but to errata the cards that have been banned (as well as some that are simply way too weak -
TWoaL,
O Elbereth! Gilthoniel! thanks to alternate RBs are my main thoughts in that area). I know it may not be possible, but I'd try to give it a fair shot.