You can have the heart of the installation ( the heater and pump) out in 10 minutes ( dependant on where you fit it).
The timer could also be disconnected quickly.
You could leave the air ducts, main wiring and exhaust in place for a future owner to install the heater unit of his choice later.
There's quite a lot to do when installing this gear -
1. ducting runs have to be kept short to prevent back pressure on the distributor fan. Holes are 10 cm so require careful siting and installation. Cutting new holes in bulkheads!
2. Fuel line has to be cut into the diesel tank so it doesn't leak
3. Exhaust pipe, doubling as combustion air intake needs careful planning - there is a maximum length before back pressure problems arise, and it gets hot, requires a special fitting on the transom, up high, to provide ingress. Everything heat insulated!
4. Electric power source and controls need routing and fitting to a bulkhead.
A lot of this gear cannot be removed again without the boat looking a shambles.
Not sure I would be fitting a Webasto with the intention of removing it anytime in the future. The new owner wouldn't exactly be overjoyed at the prospect. Can't imagine that the hard-bits-to-install are very salvagable.