Thanks for taking the time to explain, I understand.
The purpose of using content control and it's alias/key is kind of defeated if you also have to enter it in the alt-text. The alt-text is there for another purpose - screen readers - not sure how it'll act with variables in there, but guess I'll find out.. Seems like a bit of a hack currently, but I also realize why you'd do that initially :)
Sadly I'm on Advanced license, so I will not be benefiting from the added feature in the future.