More rules for dumping resources

For example, when filling in holes after extracting resources or similar, soil, rock and slag are simply mixed together. Ultimately, this does not look appealing, as it results in many unsightly grey patches scattered across the map. I would like to see an individual rule stating that only soil should be used for the final layer or above a certain height. This would make the end result much nicer and greener, and it would look more natural.

I mean, you can do this today (and I'm in the process of doing this in a few different sites) by doing the work in stages with two different mining control towers.
One tower has a work area that contains the initial work and has a given depth at a height below where my final surface is. That height is 2-6 (typically closer to 6) tiles beneath where I want my final height to be. That tower allows for the dumping of rock or slag. The second tower allows for the dumping of dirt or compost, and as I finish one area with the first tower, I change it's work area, reset the dumping height on the area for dirt, and then set the second towers work area to there. That way I always have at least one area to dump the hard stuff and one area to dump the soft stuff. I also have a large contained area for excess dirt at the start of a project (excavated top soil goes here) and when I'm done and normalizing, it gets excavated again and hauled back to restore the environment.

Certainly missing the options to have mining/dumping designation allocations dependant on their mining control tower, but then again, you can’t dump and dig on the same spot. It would be nice to have dumping allocations be height dependant, though, even as different zones of control.

You can restrict on a tower by tower basis what that tower is allowed to dump. If you block global dumping then it falls into towers zones of controls what is permitted to dump where. More than one tower can have control over a given tile, the combination of which results in what can be dumped on that tile... So you probably don't want a dirt/compost tower sharing space with a rock/slag tower.
There is a mine-or-dump command, you can place it with "n" (normalize). It'll make tiles green if they need dumping or yellow if they need mining, and they will dynamically change color to indicate which is needed. So if you normalize a tile that is currently +5 to +4, it will be mined down. Once it hits +4 it will turn green. If you then dump something there (stacker or whatever), it will change yellow again and get queued up to be mined back down.