Dynamic icon for three button

My plan here was to update the buttons used in External Compare and Merge Tools. The script stores the the path to the compare/merge tool in a global variables. I want to have the icon change based on the path being set. Setting the icon to colored if the path is set and black and white if not set.

The problem with this approach is I store the compare and merge paths in separate variables.
Having a single button will be miss leading, the icon will only be based on the compare status not the merge.

This brings me back to wanting to have the icon for a three buttons equal to the left button.
Would this be possible to add as a feature enhancement?

Regards