You could make a custom screen to handle the different tools.
Make 10 User DRO's to hold the actual tool number.
Say you put tools 13-16 in slots 4-7.
In your M6Start macro, read through the 10 DRO's to see if the tool number you're using is in there, and have the ATC load the correct tool.
So, if you have T14 M6, then your macro will read the DRO's, find out that tool 14 is in slot 5, and load tool #5, which will actually be tool 14.
Does this make sense?
It's similar to how our Morbidelli router works. It has a setup screen where you tell it which tool # is in which slot.