There's been loads of discussion around this in many threads, and I would always defer to Norbs, but here's my attempt...
Scoops are essentially trying to reduce the weight whilst retaining rebound, and as Nick says, are the beginning (or extreme endpoint depending on your point of view) of concaving.
The classic GN scoop removes weight from the centre of the bat, while allowing extra thick edges, but crucially, the removed would should be removed from the soft, un-pressed willow in the back of the wood to retain the rebound of the front of the bat. If this scoop is too deep, you will suffer from a bat with absolutely no middle. In theory, by applying the weighting of the bat around the edges and pressing it properly, you shouldn't lose power.
By way of the other example, if you were to attatch 2lb10oz of Willow about two bricks long and fully cuboid shaped, properly pressed, onto the end of a longish stick, and call it a mongoose, it would probably work quite well, and wouldn't necessarily need a traditional spine!