153's are also prohibited Southampton - Portsmouth, again I believe the problem is with the extra crew ladder on the No 2 (small) end, which is different to the original kit and at the 'proper' cab end. I've also heard that there are potential issues with a roof-mounted water tank which can cause excessive body sway and cause the coach to hit station canopies, but that could be cobblers!?
With regard to the DDA mods, I would tend to agree that the best option may well be to simply use the 153s as a centre coach inserted into 150/156 sets to boost capacity, particularly if there are other structural issues which will limit their future lifespan. This would drastically reduce the overall compliance project cost whilst still allowing the vehicles to have a useful function, though obviously extra stock would be required to replace them as individual units within TOCs' fleets. In theory this would mean no major work would be needed, other than simply removing or plating over the cabs, windscrees, exterior lights and destination gear, creating essentially a powered centre car. FGW operated a 153 coupled to half of a 150/2 unit on a semi-permanent basis for some months, so there should be no major issues with inserting a 153 into the centre of an existing unit. We also see spare 150/2 vehicles being used as centre cars in 150/1 sets, rather than being reformed into seperate units, so the precedent has been set in many ways. The problems of route prohibition and crew traction knowledge are all rather trivial in the grand scheme of things and could be easily addressed.
