I'd argue it would be smarter to upgrade CE to meet modern standards than creating a branch of id's software while porting all of existing Bethesda tools.

we don't have access to the source so we can't really say things are bolted on. it's also possible that code is removed as it's made obsolete.

I don't think you would have to create an entirely new engine to support elite dangerous type of warping, or elevators even now they could make the illusion better