It is reassuring to know that the seller appears to be willing honor the return guarantee. Hopefully we will still hear from Michael or one of the others who might be able to help.
Is there a machine shop near you? If so it might make some sense to show the camera to the machinists, and demonstrate the issue you identified to someone at the shop. They might be able to offer a relatively quick and effective solution that would not be too costly. Again, your solution might also work. However, before doing anything to the camera, take some photos of the camera as you receive it and be assured that the seller agrees with any modifications that you are planning to complete.
Happy to be of any small help. I hope that the camera can be returned to good order, and that you can use your KMV for many years to come.
Incidentally, there are very few sources from which one can purchase lens boards for the KMV. Michael and Paula provide what are probably the best KMV lens boards currently available. You can contact them directly.
Don't give up quite yet...and of course, there are alternatives to the KMV.....:}