I’ve personally implemented vehicle pooling with fgear years ago with unreal4 so it is possible. I don’t understand what your problem is, you need to basically re-activate everything and put it back.
you can manually sleep or wake a vehicle by calling vehicle.sleep/vehicle.wake functions but even if you make it sleep it may wake back up due to any collisions so you can’t force a sleep. try calling sleep, disable all ticks including all components, disable collision etc. and revert everything when you want to respawn a vehicle.