This engine is already great for modding, but I suppose it can always be better. Do you know any technical details about why the worlds can’t be made seamless? There were open cities mods for Oblivion & Skyrim, so it seems like it’s probably technically possible. Seems like that may be more of a compromise related to memory allocation on consoles.
I dunno, I don’t expect Bethesda to write a new engine from scratch, no one does that. They made New Atlantis seamless to an extent I haven’t seen in previous Bethesda games, so as long as they keep making incremental improvements, I’ll be satisfied.