Tileset Per Layer

I would really like to see a Tileset per layer controls for Pyxel Edit.
I would like to have a couple layers in my tilemap:
Background: Set to my Background Tilemap
Dungeon Elements: Common elements used through all my dungeons
Dungeon: Specific pieces for this dungeon
Something like this:
with a place to make new tilesets in the layers Options
I feel like this would greatly expand the usability of Pyxel. This way I could re-use tilesets throughout multiple Pyxel documents while still exporting and using the same image set.
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