I use the word functional instead of usable or controllable because that’s kind of under the umbrella of how they could be implemented.
Both Fallout 3 and Fallout 4 had rail systems you could see moving (the presidential metro and Nuka-Express) opposed to Fallout New Vegas (Camp McCarran’s monorail) for example.
I feel like the two major concerns would be how their addition would effect map design and how the engine is going to handle them.
I know what you’re talking about, however, I think that any kind of limit that they could practically set in order for it not to screw with gameplay too much would kind of suck all the fun out of it, defeating a purpose. Ultimately, there would need to be some sort of balance, and I think that balance might just be too hard to find.
It might be interesting to experiment with it though.
That’s probably how they just settled on the teleportation device.