Well, that post was a day ago
Now I can do basic selection (a square). Expand all directions. (L, R, F, B, U & D). Set the selection in 1 blockId(and metadata) or in a randomly determent pattern (like this: "1%46,5%36:2,70%1" and it fills the rest of the % with air.) I can save and load regions (not relative to player yet).
And I make backups! (No undo yet though...) So, I'm making progress.