The Idea is to add revisions to the collections. At one point i f*ed up while managing my collection and it would have been nice to be able to go to an older version (it's more critical with collections than with decks i think, since collections can hold thousands of cards). I don't know if it should work exactly like the revisions for the decklists though. I think collections are modified way more often then decklists, and way more cards are stored in it. Maybe a simple changelog might be good enough.