As of SAM 6.5 and I'm assuming more importantly Core 2017.3.4 you can now use complex variables in the TO: field of a send email action in advanced alerts!
In the below example we have 2 custom properties on groups. One property holds the email for that group (group_email) which is where the alert gets sent. The second property (Is_Distro_Group) is a bit (yes/no) custom property that determines if that group is used for alerting. This was needed as we have other groups that aren't used just for alerting and we needed a way to differentiate them.
For production use you would want to change the EntityID=1 to something like EntityID=${N=SwisEntity;M=NodeID} This would allow the alert to identify the group that the node is a member of and use that group's group_email property to send the alert
In the container table EntityID is not just for nodes, so its important to filter to whatever you want for your case as you can see by EntityDisplayName='node'

At any rate we are very excited this works now. We can finally scrap our custom send mail action which was an ugly external vbscript!
Message was edited by: Ryan Davis - changed EntityID='${N=SwisEntity;M=NodeID}' which wouldn't work as single quotes around the nodeid variable doesnt work to EntityID=${N=SwisEntity;M=NodeID}