You see, the Cryptolocker guys are actually smart criminals. They did not, as you assume (and in doing so, greatly underestimate their cunning and intelligence), enter your supposed infinite ransom loop. Instead, they decided that keeping their word was in the best interest of their "business plan", if we can call it so. They established a weird kind of credibility, where the victims knew paying was the best option, bar none at the moment. And then they delivered.
But here is the big difference. With Cryptolocker you deal with one attacker with a certain identity, so you know they behave in a certain way because they did it in the past. In an P2P exchange you will not make the trade with the same person again (the bank details give the identity). So there is no reason to assume when you onced get blackmailed and the blackmailer acted "honest" that the next time another blackailer will do the same.
That doesn't change anything. Criminals can provide PGP keys like anyone else.
Anyway, I don't wanna derail your thread, but I urge you to not forget this issue and seriously pour some thought into it.