A nice thing to have would be :
... Freeze , Pause for overall ZM engine ...
The purpose to have this ,would be that some functionalities would still be possible , but not writing into the database .
This in order to get a lock on the tables so a quick backup of the whole db can be taken (trough LVM snapshot ,so that this takes a very limited time).
For people who can't afford loosing recording minutes ,this can then be rerouted for this period using a failover ZM system.
I use this kind of working very effectively on a CMS system where the software enables us to do a 'freeze' on its file system and software.