Possibly yes - I can see where you're coming from. But remember that parts of the seat ( foam bits ) are glued to the frame etc.
I have a welder so I'd be more inclined to modify the seat. However, I agree it's a bit 6 of 1 ...
I'm with Clive on this one - having actually done it
I had cloth Spider seats and leather GTV seats. It was easy to take the seat apart and swap all the upholstery onto the Spider seat. The glued parts are not difficult to remove. I remember a bit of surface rust on the seat pan I was using, as the black paint wasn't as good as the other, but nothing major.
Might still need the welder for one thing, though - the 'wings' (made out of bent rod), that support the base side bolsters, tend to have broken off the seat pan, but can easily be welded back on stronger than before.
The foam that fits over them is probably ripped and shredded. I used some expanding foam spray of the soft white type, with cloth tape where it needed reinforcement. But another time, I think I would just cut new foam to fit and tape it onto the support wing. Ideal solution is if you have a spare passenger seat and can use the less-worn foam from that.
Anyway, the seats are easy to take apart. Yes it's a lot of work to strip four seats for the sake of having seatbelt runners, but worth it to clean everything as you go and fix the foam/bolsters etc. in the process. Also a good time to reduce the thickness of the foam under the central cushions, which makes the seat more shapely and supportive.