Wingback arm chair

Nope.

I can't speak from an MOT point of view as I am not a tester, but safety-wise its a bad idea. Firstly, these things are wooden framed, and pretty flimsy too. There is no way to easily fix it to a car floor securely enough so that it wont just pull apart in the event of a crash.
Secondly, the shape of the seat will hold the seatbelt quite far away from your body, so even in a minor bump you will shoot forwards before being brought to a sudden stop by the belt, or even just sliding under it. This is the reason its not advisable to use a normal seatbelt with many bucket seats.

If you used a multi-point harness and cut suitable holes, and reinforced them at the relevant points to allow the belts to pass through, removed the entire wooden frame and fabbed a replacement in steel, then refitted the padding and cover, then maybe it would be ok. Maybe.

its also probably about a foot wider than a normal car seat too

Actually although I think the idea is horrendous it might be possible. Look at the seats people make and fit into hot rods ? Timber frame isn't such a negative as it was a common method for the seat frame on "quality" cars in the past. Morgan still have timber body frames, early Marcos had wooden chassis and Morris Minor Traveller had structual timber so it is well used in vehicle stressed areas.

Paul h