The initial idea stems from not wanting to get emails for known things happening to machines being worked on.
As I thought about how LEM could easily do this....I did have 2 ideas, but open for others:
One
From Manage-Nodes, selecting a Node and Placing it into Maintenance Mode would:
Automatically add criteria to the Rule Engine that in a sense said "if this stuff happens AND IT IS NOT THESE NODES, than still take the Action".
Two
I suppose this could be done today with a User Defined Group. You would add Nodes to this UDG (let's call it Maintenance Nodes). Then you would just have to add that line to every Rule. If you were going to add it to every Rule, that is where the "built in" request comes in.
Scheduling these would be a great bonus.