Can't remember where I read this, but I think the main problem is the UE build tripwire has for RO2 does not have alot of the components that allow for GNU/Linux support which is in current versions of UE.
I think a game as moddable as RO2 would very much benefit from GNU/Linux support because you tend to find alot of computer savy people using the system, and they like tweaking things. Knowing that tripwire I don't think would ever make an unmoddable game, they should consider making it part of the plan for future games.
Also, and I hope this is taken as constructive critism, a more data driven model of programming would help make modding the game alot easier and more customizable
Ex: not having skins hardcoded in GameInfo files.
I guess their could be reasons for this but my 2 cents, thats all.