i think brian is totally wrong there.
almost every commercial jeep you see in this country started out as a passenger model. in a lot of cases the seats/glass gets ripped out by the importers. although it sounds crazy, the commercial jeep idea seems to be a purely irish phenomenon and the relatively small volumes would make it uneconomical for the likes of toyota, nissan etc to bother with it at their factories.
the vrt will be charged based on how the vehicle is presented to the tax office.
afaik, you must remove the seats , block out the windows, put a plate over the footwells and weld up the seatbelt anchor points.
if you subsequently undo these modifications you would be liable to pay the vrt difference although im not sure who checks this.
there used to be a loophole where people used to tax passenger jeeps commercially but this has been done away with as you cant get a doe if the welding mods i mentioned above have not been done.