I have found a much simpler way of achieving what I was looking for in a MailMate-adapted workflow.
Apparently MailMate has it's own URL scheme (see here). It is easy to compile a simple workflow (or web search) in which mlmt:quicksearch?string={query} is entered as the URL in an Open URL action triggered by a keyword such as mmt.
MailMate searches can then be initiated from Alfred using the same search syntax in the Alfred search bar that you would use in the MailMate search box. If, like me, you search in MM many times a day, this shaves several clicks off each interaction and makes for a more comfortable typing experience. It is also better than a multi-keyword approach since, it keeps the search syntax consistent across apps.
Probably obvious to many, but helpful I hope to some other MailMate users.