Converting a panel van

[CM07DAY]

Hi everyone, I am new to the forum but not to transits. Had a few in the past but mainly mk6 350 lwb.

I currently have a mk7 125 jumbo that I've rebuilt the engine and pulls like a train, very happy with how it drives. After lending it to my brother, he has slightly modified the rear n/s top corner, when I say modified I mean annihilated! The rear door will not open as the roof has caved in around the door. This is deffo uneconomical to repair, however........

Im now thinking to remove the rear panels
my idea is to fit and weld a full height bulkhead behind the cab then brace the bulkhead to the inner rear wheel arches to keep it straight and help structural integrity during the fabrication. I would then cut the panels behind the cab following the bulkhead line then along each side where the floor meets the sides, leaving a type of chassis cab. Then fabricating a rear 'box' directly onto the chassis using box section and grp sheets, or fitting a Luton body directly to the chassis. I want to do this as I might camper it and the extra space and straight walls make a conversation much more appealing.

The reason behind this is that firstly, I never intended to sell this van as I know the engine and gearbox, and all round mechanically is sound. Secondly I don't want to use a chassis cab as I want to keep the lower floor, and lastly I used to be a welder fabricator so can do the work myself.

What I want to know is any legal/dvsa issues I might have? Weight shouldn't be an issue, if anything it should make the van lighter as I won't be using a tailift, just a rear outward opening hand door
Any constructive feedback would be appreciated

Thanks in advance
Chris