Looked into buying one of the systems.
Blakbox used to do a rovacom which you could add units to but this has been replaced with the Faultmate SV system which is VIN specific and only used on one car. The Faultmate MV can be used on any number and has a price tag to match but if you have a spare £8k spare why not treat yourself to an Autologic system which is what most independent garages use.
You need to work out how long you are going to keep the vehicle to the number of times the electrics go bely up.
I have a 2002 ES which is fully loaded and lifted 4" steel bumpers and sills winch etc, full prep and the abuse it has had off road I have had no problem with electrical systems at all.
Best thing is to find someone local to you that has a system you can plug into.