From the beginning it was Mageia's intention to _not_ have unofficial packages. Instead it should be easy for any packager to become an official Mageia packager, with the right to package any software (that doesn't have legal issues) and the right to push any updates. That way, local communities wouldn't need unofficial repositories. https://wiki.mageia.org/en/Becoming_a_Mageia_Packager
Did the users for whom you sent this mail feel unwelcome when trying to become an official Mageia packager? If so, my apologies, that shouldn't have happened. Or is there a different reason why they aren't Mageia packagers, yet? I very much hope we find a way to solve that.
Note that allowing unoffical packages with «mga» as distsuffix makes life much harder for BugSquad: instead of only asking for the SRPM we'd have to also ask to check whether the buggy package was signed by Mageia. Besides, QA team doesn't test whether our updates break any unofficial packages, nor whether unofficial packages break upgrading.
Kind regards, Marja