This is possible with the new version of CJOverkill. Couple that with Icefire's new CJO Tsunami program and you can run as many sites on as many domains/subdomains as you choose.
This is his demo/test setup, but check it out. He's got about 200 or so TGPs that are all managed from one back end.
http://blowjobs.weather-condition.com/cluster.php
http://cjoverkill.icefire.org if you want to check out the ALL-NEW CJOverkill 4.0.2
More details on Tsunami can be found here:
http://bbs.icefire.org