I've tried getting VSOM HA members to 'do other things' in a lab environment, but not a maps server. I believe there's some back-end logic that actually checks for any other roles and shuts you down pretty quick if you try to configure it.
I haven't tried any maps servers, so I'm not really familiar with them, yet.
Cheers!
Scott Olsen
Solutions Specialist
Bulletproof Solutions Inc.
Web: www.bulletproofsi.com