I thought aircon Mk3s couldn't be pushpulled with a Mark 3 DVT, unless the idea was that the coaches be wired for it during refit? In any event if 071s or 111s had to be used then they would have to haul anyway.
Presumably a refit as significant as this would not make an accessible toilet a major extra spend, but
aren't the doors an issue too, as it was for Chiltern? Or would a service such as this be able to plead an exemption of some sort?