We do the same thing, custom views, mostly drawn in -drawRect:, reused in different cells. It's actually a very nice technique but like you said, the are some sacrifices to take. Still, these cells depend of a tableViewcCell which has unique properties and special APIs that collectionViewCells don't.
I think the most trikcy part here is to be able to build a custom UICollectionViewLayout allowing to display cells from the bottom. Haven't found any third-party doing it well enough yet. Do you know of any?