It’s only going to be as strong as a Range Rover. The seat itself is a safety feature. It has 6 bolts that connect it to the rails on the Range Rover. As long as you use the 6 bolts then there is no reason that this should be any less safe.I like the idea of this, but knowing the seatbelt buckle is mounted to the seat rather than the base, I would be more concerned with the strength in an impact.
Additionally you can use a seat belt clip that’s not attached to the seat, I used the one from the middle seat for a couple of days whilst I was fixing it.
Finally, as mentioned. The start line T6 has a dumb seat. No air bags no nothing. So the vehicle cam is does control anything like airbags etc. So again no less or more safe.
If I was going to do it all over again I think I would be tempted to get a large square welded to the base and then get the holes pre drilled in to position.