(SNES) priority map image for non-mode 7 tilemaps and mode 7 extbg tilemaps

[H-A-M-G-E-R]

maybe black is low priority and white is high priority
and make it the same size as the image

[nikku4211]

Can using an indexed input image with a 256-colour palette where the bottom 128 colours is a dupe of the top 128 colours work well enough as a workaround for mode 7 EXTBG?
The problem then would be visually keeping track of which pixel's colour is from which half. You'd probably need to tell SuperFamiconv not to remap colours for this workaround to work, too.