It would be helpful to have the ability to override user-defined macros during maintenance periods. 

For example, during maintenance, you will shut down one of three servers. The remaining two servers might experience a bigger load. It would be nice to adjust thresholds (which is a user macro) at that period of time. 

Another option - suppress trigger by adjusting macros for a certain amount of time. Since you are waiting for more servers, the current ones are under significant load. And you don't want to adjust thresholds on hosts; you only need to suppress them temporarily(via rising thresholds) .