Good point.
However if conversions like 'left to right' are of concern then a lot of people in the Classic world are going to be affected and it will be a nightmare for the authorities.
I would also suggest that there's a good argument to say that the conversion of a Z is non-structural as it can be done without chopping the bulkhead about; most of the changes involve removing and adding/shifting spot-welded components (with the exception of drilling the steering and master cylinder holes and welding up their LHD equivalents), rather than interfering with the structural integrity of the bulkhead, which is what sets off the DVLA.
Alternatively, Woody's complete bulkheads offer another solution that retains total structural integrity and factory correct look. Any DVLA entanglements (in the rare likelihood that it got flagged, which could only be through self-incrimination as it would look original) can be rationalised by the fact that repairs are allowed to shells. As it happens, my project, which will be RHD converted, has rust damage to the bulkhead in the battery tray area (unfortunately I discovered evidence of perforations yesterday), so if I went down the route of bulkhead replacement, there is a demonstrable justification. Under the points system, you might lose 2 for switching left to right; the aim is to not lose the 5 for the body shell.
Some cars require much more chopping and reshaping and run a risk of being flagged IF caught (Porsche 911 guys are worried for a start). And that is the thing - as with all British bureaucracy, volunteer the bare minimum of information to them and certainly don't proactively ask questions, lest you bring a world of unnecessary hurt down upon yourself and other owners!
I continue to obsess and read over this whole MOT change issue, and tbh, I can see a good likelihood (hopefully) that what will happen will be that for the majority it will just be a case of requiring an MOT to tax if you declared your car modified. There will be so many owners ticking that option that it will not be viable for the DVLA to pursue everyone for clarification. They don't have the time and resources. Thus, it will become a non-issue, unless someone is really obviously taking the pi55 or they engage in random spot checks.