Hybrid texture maps

[velojason]

I've been messing around with the Flat maps maker in GRF Editor but am curious about something that seems a little beyond what the getting started type of tutorials cover.

My dilemma is thus: I love RO's art style, colors, and textures but I also love the visual clarity of walls, dead space, non-walkable, and non-snipable tiles in a graymap.

Is there a way to blend them? It doesn't seem like I can tell the flat maps maker to only convert the dead space tiles. But it's also not immediately obvious to me how I could go about changing the textures manually. I have to imagine there is a way, though.

Anyone here have a nudge you can give me in the right direction toward accomplishing this?