I'm really struggling to see what the problem is? It appears pretty straightforward?
If you regularly take a partner or family member to a MSCC event, then take out joint membership (at no extra cost) so they are named, and then they are fully covered by MSCC event insurance and can also take advantage of other member benefits.
If you don't, then it doesn't effect you at all.
MGOC has an approved insurer - Adrian Flux. However in previous years it was Lancaster. This year I insured again with Lancaster and my renewal was £95 (Fully Comp, protected NCB). Flux were advertising that they would beat any quote by £25, but I didn't have the heart to call them........
I insured the Mog with Gott and Wynne this year, and they were comparable with last years Footman James policy (which had increased). There are many specialist Classic Car Insurers out there, that insure all different marques, so I doubt the MSCC arrangement will make a blind bit of difference.