I like these ideas, you’d have to raise them upstream with the Plank developer(s) to see if other users (including those outside of Ubuntu MATE) have also requested similar things.
For #2 - it could be possible there’s a program out there already that can launch a full-screen grid of applications.
Another (slightly bug) I’d like to add is that under Compiz, the window snapping doesn’t quite work like it does with a MATE panel or other window. 