PB,
These units mostly come from Staluga, which is a submod for Bulat Steel. Bulat Steel is based on SS6.4. The original models came from other mods, but they have been altered to fit the expanded faction rosters of Staluga and to provide upgrades for units, such as those imported from Broken Crescent, which have no upgrades.
I have put these units into some of the factions in my SS6.4 with BGRV. However, I used a quick but gigabyte heavy method of doing so. I copied the entire unit_models folders from Staluga, Broken Crescent, Bellum Crucis and a few other mods into my SS6.4. I then renamed the unit_models folders to, for example, stal_models for the folder from Staluga. I also renamed the battlemodeldb for each in a similar fasion (see attached image). I was then easily able to copy and paste the units I wanted to import into my SS6.4 from the battlemodeldb of Staluga or the other mods I wanted to import units from. But once again, this is probably not the proper system to use for RR/RC Ultimate Compilation, and of course you would have to get permission to use the entire unit_model folder from the creators of Staluga and any other mods.
A better idea might be to contact Achilles-91. He knows more about these units and others, and the modders who made them, then probably just about anybody, I think. Not long ago he was working on a huge project to upgrade the units for SHHIP with new rosters and models. Perhaps with the release of RR/RC Ultimate Compilation he would consider a simpler project of just working on the eye candy aspect. Unfortunately, I am far too busy with work to undertake this project myself.