This is a possible feature that I have code for.
The idea is basically to extract the action icons from the core enrolment to the enrolment plugins API.
While there are no plugins that would presently need to override the default (edit if editable, unenrolable if possible) it would mean that future plugins could add additional actions there if they so choose.

This code requires the changes in MDL-23532 to be integrated before it can be integrated.

Cheers
Sam