What are you actually allowed to do modification wise? Can you drill holes in the floor for GrippaMax?
Can you install a Flettner?
Cut a slot in the floor for hose rollers?
I tried to look for it but can't find a definitive answer.
Because there isn't one.
Back in the days you could fit a Flettner but it had to be done professionally (usually by the supplier) and it would be left in at the end of the contract. A Flettner wasn't seen as reducing a vans value and/or chance of sale at auction.
I think Grippa had an agreement with Kennet? that they could fit a tank to a lease vehicle supplied by them. I'm not exactly sure what happens to the tank at the end of the day. I presume its part of the lease so left in the van at hand back time the same as BT leave all their racking behind when the van is due for renewal.
Back in my motor trade days councils would order a van for delivery just before a tax year ended. They would pay cash. The value of the van would be a tax write off. Then at the beginning of the new tax year they would sell the van to a leasing company
and lease it back with all its fixtures from the leasing company.
At the end of the contract the van was sent to auction with all its fixtures still in place.
I would imagine you would have to get written approval to have extras fitted like hose rollers and they wouldn't approve you doing the job even although you would do a better job.
You might be able to fit a roofrack with permission but a towbar could prove to be problematic. Someone could argue that towing a trailer could have increased the wear and tear element of the contract so make you subject to penalties.
There are leases where you take the risk at the end of the contract. If they valued the final balloon payment at £7000 and the van was only worth £4000 then the difference is from your pocket. You could opt to buy the van at the end of the contract but usually that becomes another loan against a further depreciating asset. If a builder wanted a van on lease they had the initial payment increased considerably and no balloon at the end of the lease.
At the end of the day if you decide to lease you have to ask questions about what you can and can't do before you sign on the dotted line.