I had accepted this as impossible for the past year and a half, and on a whim decided to see if I could find anything new. This is going to simplify my profiles a ton! Thanks!!!
This label is completely possible to construct without any workarounds: (see attached image)
In your structure label, add a Reference Text, select "alignment", and put in the same information as in the first component. (Add an equal sign if you wish.) When you attach the label, it will insert the station and alignment name that the structure itself references. Then, in the command line, it will ask you to select a second alignment that you wish to reference. Select the second alignment, and Voila! A totally dynamic, dual alignment label.
If you are applying the label in a plan sheet with Xrefs, I'm not sure if you can click on an Xref'd alignment to get this to work. I do know that it works if you have the alignments data referenced into the file. Someone test this and let us know.
Never mind... I just reread the OP's question and realized they are referring to profiles. My bad.