If the issue was that the barrels were so close together that H&H couldn't be reworked to take the true flanged case then sleeving the H&H chamber to remove the H&H belt but leave the H&H rim would be the perfect solution. When the bushing was rebored it would have to be set to force the headspace to the H&H rim and not the shoulder.

Keep in mind on the cases you are turning off the belt and not the rim.

And again you would have properly marked barrels with properly marked cases for those countries that check that. I don't think they would notice that the belts were turned off the cases.