There is no esp/esm incompatibility, Oscape only sees colour textures when they exist as forms in the same plugin as the worldspace. You can workaround it by merging your landscape textures into your plugin containing your worldspace, and only using those.
That sounds messy... Perhaps Ethatron could make a fix to allow Oscape to see texture forms outside of the worldspaces esm/esp? Pretty please?

(I can't repaint my world with new forms; I've already generated all the regions and started editing them)
I don't make that kind of stuff, just programs. What is helpfull is to provide me a test-case where you know the outcome. Make me a little esp, make it dependent, generate the files with the CK so I know how they should be after generation, package esp, LOD files, landscape textures, everything I do not have. Then you give it to me to debug through it.
I'll upload my mod with all that in the chance that it helps you.

Though,
correctly generated colors are like 200mb total, so this may take a few minutes. **Oh gawd nevermind they zipped up into 35mb total, for my mod and all the LOD stuff. Hopefully this can help you work out a solution. (Also, I trust you wont share this with anyone and will delete it all promptly and this is an unannounced project.

)
I'll message you a link when it's done in like 3 minutes. **Sent!