people always slate the trader-in reality he probably hasnt a clue the car has had abs removed...there are new parts creeping into the mot laws year by year -very easy to catch somebody out big time now,potentially writing a car off.
it is common on mitsubish evo to remove the abs and change it to an rs set up to give more predictable braking when sprinting the car as well as reducing the weight[done it myself] -with a lot of cars having the ayc removed for a mechanical diff too-will these cars ever pass an mot now[a strict one anyway]
i would have thought the van is fit for purpose[transport] as it starts stops
however it "probably" should be able to pass an mot...the fact the garage had to delve further into the facts it is obviously not a very apparent issue

good luck with a solution in your favour