MORA, can either be route MORA or Grid MORA.
Generally this will be used for emergency, to make the calculations of this easier.
I think from the JAR definitions, it is not the MOCA you should use for emergency, it should be the MORA. Specially grid MORA, you need to check what grid you are in, check the adjacent grids, and use the one that is highest!
You can also use route MORA, but this will give a much more narrow band to work with, as you just explained.
To be honest I think MORA is the one you normally would use for emergency, not MOCA.