The modding part wouldn't be that difficult. There's several indie titles out there where the developers added modding support. Insurgency Sandstorm, and Mordhau are a couple examples among a strong indie presence of games built with UE4/UE5. If indie teams can do it. So can Bethesda. Not too mention UE5 can be tuned to work better with teams, that can be done with programmers as Epic Games has made the full source code available for those who need customization on their side. Epic has UEFN or "Unreal Engine for Fortnite" which allows gamers to make their own content for Fortnite. I've seen total conversion mods released for Fortnite with these tools. It can be done.
