I bet it would be possible to stitch together and bring the maps of Enroth, Antagarich & Jadame, from MM6, MM7 & MM8 to Garry's Mod. You'll probably have to use a Quake 1, Quake 2, Half-Life 1 and Quake 3 Arena map editor to make a Quake, Quake II, GoldSrc and id Tech 3 version of Enroth, Antagarich & Jadame, from MM6, MM7 & MM8 to bring it to GMod though.

Now call me mad, desperate, depressed or insane, but I guess if Ubisoft won't bring the 3DO/NWC Might and Magic games to Steam, then GMod conversions of them will probably be the only way to experience MM6, MM7 & MM8 on Steam, unofficially filling the void and gap in lieu and in absence of an official Steam release from Ubisoft.

You'll probably have to use a Quake 1, Quake 2, Half-Life 1 and Quake 3 Arena map editor to make them, and port them to Source engine to make it a GMod map though.