Make a module read-only except for one field

I think I know the answer to this one....but asking on the chance that someone has a snazzy shortcut or answer.

On the Account module, we have a "critical customer" field that anyone in the organization can check and it causes a message to immediately go to the entire company.

For most roles in Sugar, we want to secure the Accounts module to read-only for most roles except for that one field. 

I tried securing the module by setting edit to "none" and setting that one field to "read/write".  

As I expected, the module-level security overrode the individual field.

I realize I can set the module to allow editing and then lock down every individual field except that one field....but is there a better/easier way?  

I appreciate any thoughts/input!

Bob