Instead of keeping the screen preview in the palette editor, make it a whole system (a separated window?) that can read in the ROM and use its font data instead of precomputed graphics.
It allows to have a "live" preview of both font and palette edition, to alleviate the palette editor of one of its tasks and, why not, having CLI and GUI commands to generate a preview and save it as a picture.
Instead of keeping the screen preview in the palette editor, make it a whole system (a separated window?) that can read in the ROM and use its font data instead of precomputed graphics.
It allows to have a "live" preview of both font and palette edition, to alleviate the palette editor of one of its tasks and, why not, having CLI and GUI commands to generate a preview and save it as a picture.