I suspect this will put a lot of weight over the back axle, you'll probably get pulled for this. You'll be within the overall payload weight for the vehicle, but that weight must be evenly distributed. Each axle has a weight limit, exceeding it is against the law and unfortunately very easy for the coppers to spot.
I faced a similar dilemma 18 months ago. I needed a bigger van but also needed transport for non-work use.
I opted for a new Toyota van with a 700 litre ionics pure2o system, and also a car. I'm glad I did to be honest, I don't want to use a work vehicle for getting around in, going shopping, going on holiday etc. You need rear seats in your private vehicle IMO.
However, I am now facing yet another dilemma. New business is continuing to come in at a strong rate, and I now need another van on the road (so I'll be operating 2) but having 2 vans and a car seems a bit much. Then there's the problem of parking...