Are you saying you want "webmaster" accounts for each virtual domain? The thing with virtual domains is that all of the domains' accounts are all actually accounts on your one server, whether they're for domain1.com or domain2.com or whatever. I thought someone posted here that you could create different accounts ("bob" and "sam") with one for each person administering a domain. Then set up pseudonyms for admin@domain1.com pointing to "bob", and admin@domain2.com pointing to "sam".
I think it was posted that you can do that, but I have no firsthand experience so I can't say for sure.