Quote posts would be allowed, but count against your reserve of posts without increasing it. You want to spend a post snarking on some troll, that's fine, but you're going to have to balance it by boosting a post sans commentary.
If a system like this were really going to promote better engagement, though, I think replies to (and quote posts of) your own posts would have to be excluded from your reserve. Otherwise, people would just build up their reserve by boosting people who've agreed with or said nice things about them. Those would need to be reserve-neutral.
It would definitely promote a different type of behaviour from users, and a different type of messaging.
Merveilles is a community project aimed at the establishment of new ways of speaking, seeing and organizing information — A culture that seeks augmentation through the arts of engineering and design. A warm welcome to any like-minded people who feel these ideals resonate with them.