The game would be the same as Capcom vs Marvel. 1 game, that contains all characters. Stories dont have to make sense, its basically a Tekken Tag lookalike.
I like VF, I just think that the characters move waaaaaaaay too fast to be normal, Tekken games have more FEEL to me, I can get into them easier, but I really think that fighters need to have more contact, I want the element of action movies, like Tony Jaa fights or Jet Li close fights, not this punch you, punch me routine.
But both games are similar, unlike DOA which is closer to DBZ then tekken and VF, all that dissapearing and blowing things up with magical ninja moves, the only magical character in Tekken to say the least is Devil as far as I have seen. So a Tekken vs DOA game wouldn't work. DOA characters look too anime, and Tekken characters don't have exaggeratedly large breasts, the combination would require a significant amount of changes to both games before they could fuse.
Besides, Itakagi hates Tekken, eff him 😛 And Sega and Namco have a closer relationship, the people making VF and Tekken are practically best mates, so they are more likely to do that. VF characters look more similar to Tekken, that type of game would work, not only that, sounds mega exciting, I hope they do do it.