Mhm. Card v Card i think is problematic... 1) a bit rare; 2) easy to read/bluff... ok, that makes it not easy if you figure in "is he going for that mission or not"... which makes it total guess apart from reasonable strategy to win a game. I think that would not be good...
The main "problem" is that it would be a bit too specific. You can get to it almost only by chance or semi-active manipulation (2 people, 1 clan room, cards in hand, make a deal... "great"
BUT I, too, see room for "story mission". There was one card who was sister of another card... how about "Sisterly 'Love'" - Win A rounds with (character 1) against (character 2's clan)? Also winning rounds with any Montana
(and vice versa) has room... and others, too. (Winning against a Cr is fine, btw: there are enough of those and the other side is "any card". But how often do you see, say, Windi Mor actually having even the chance of facing Kiki
? Boils down to random chance meeting.)
Also, there is at least one reasoning behind big prices for first missions: it supports newer players quickly. Think of higher prizes as "specialisation" - diminishing gains. That said... yeah, I too often find rewards of later stages kind of lame. On the other hand, I don't do missions for prices but as extra-challenge just to finish them. I'd do them without prices, too - maybe not even feel "l4m3z0red" at all: Ironically, if there is nothing it does not feel as bad as when there is a perceived "not enough by far".