I shall use the words of average young internet user... RHS ftw

While theorectical possible, I am personally not a mods/addons fan (mainly because those mods are huge and I don't have the internet to download and update all that).

Even if I were to, because a friend once asked me to, It would take quite a long time because I am really just a part-part time maintainer.

TL;DR It's possible but it will take a long long time.

I haven't played DUWS rebirth yet but isn't there already an RHS version of DUWS https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=377667225

I've suggested these solutions a few times now that would remove the need to make a patch for every different mod:
1. Make it so that the player can load custom troop compositions into DUWS-R. There would need to be some kind of way to calculate the value of each composition based on it's components, though.
2. A more likely solution would be to add restricted Zeus capability in a small radius around the player's FOBs and somehow translate DUWS-R's currency into Zeus currency.

I updated the version of DUWS-R I play to use RHS/CUP assets. It's not particularly difficult to do. Its pretty much just a find and replace job. i.e. replace all unit mentions with their RHS counterpart.