Hi!
I can think of many situation were readonly on an action is actually helpful.
In our case we're actually using it already using our own custom editor on specific actions, but it would be very convinient to have the actual tag (that is already in the API....) to be working, so we don't need to create/update custom editors for all the actions.
As far as I know, Tooltip is not really an options since you can't pass a method to it, needs to be a constant expression...
Thanks!