But why would you want straight square random gamma/hue patches on ground material? Doesn't sound very realistic to me :] Wouldn't it be better to apply same principle like above, just replace tiles map with noise, or some grunge texture? I'm struggle to think about scenario where random texture transformation would also require HSL randomisation per tile, but even if there are such, they probably are highly specific and wouldn't justify cluttering already crowded UI of UVWRandomization texmap.
Let's say you have a regular pattern for displacement, something that tiles of course, a grid for example, and you need to introduce some irregularities. I'd use that tiled map and compose a noise map over it, using a circular mask which blends to black on its borders so the noise isn't visible on tile borders. The multimap would introduce different brightness/gamma to that circular map so each grid tile center would get variable contribution from the noise.
Maybe you remember the disco tile map from cebas, it was part of finalrender a long time ago. I had one job where I needed exactly this map. This mode would allow easy creation without workarounds. Of course, it was doable in other ways but not as easily.
I don't want to clutter the thread with my own thoughts but I happen to think that a way to randomize map properties without randomizing UVs might indeed be useful.