In the game Bloodless, I limited MM by
- eliminating blood magic altogether (well, spells items and sites)
That of course reduces the number of playable nations, and we are playing in MA
- removed gem gens, some bonus sites, some rituals (AC, AN, UD, Forge) and Tartarians
- limited the number of players (starting with 6) therefore the number of provinces.
We increased magic site freq though.
http://forum.shrapnelgames.com/showthread.php?t=43298