ZDoom

It's possible with things (sprites), so there's no reason why it shouldn't work with linedefs and sectors (textures and flats) too. It would certainly be a big step forward like the thing translations were, and improve maps to no end.

Specials could be like this:

Line_SetTranslation (lineid, translation)
Sector_SetTranslationFloor (tag, translation)
Sector_SetTranslationCeiling (tag, translation)
Sector_SetTranslationBoth (tag, translation)

I think Sector_SetTranslation(tag, floortranslation, ceilingtranslation) is sufficient. No need to waste 3 specials for it. It would be a neat feature, though.

I didn't want to start a new thread and this seems relevant enough to mention here, so:

Would it be possible to implement applying an entire colormap to an object?(and wall/floor/ceiling assuming the first feature gets implemented) This would greatly reduce the amount of work needed to create an entire palette translation.

In this case, the new special would look like:
Thing_SetColormap(int tid, str lumpname, int colormap)
Tid being the thing id, lumpname being the name of the colormap lump, and colormap being the number of the colormap to use.

example: Thing_SetColormap(1, "COLORMAP", 32) would cause the object(s) with tid 1 to be rendered in invulnerability colors.

I think a CreateTranslationFromColormap(colormapname, index) will be better because then you could use all the existing logic with the created translation. Same effect, more flexibility!