It would be helpful to be able to assign a list of default action types to security groups or roles so only the action types applicable to them appear when they enter information. These users would still be able to view other action types on the record entered by other users though, as this is more of a method of ensuring data accuracy and less of an issue of limiting security. It would make it easier for users to only have to choose from a list of actions that are applicable to them instead of having to scroll through the entire hard coded lists of actions, most of which they don't use and shouldn't be choosing when they enter data on a record.