As a member of better GEDCOM and FHISO you of all people should know why it should not be used.
I don't know your background, but I agree with you that nickname is not the same as AKA it does mean also know as, but we should begin to use consistant fields for the same concept NOT continue a bad implementation.
The NAME tag has a standard place to indicate if the name is a married name, AKA, birth, etc name, FTM chooses like so many other times not to use a standard form.
So instead of asking to expand the AKA field to include surname, ask to add "type" value of AKA, married, birth, or other to the NAME field.
This is the GEDCOM standard, and would support proper GEDCOM transfer from my program, a GEDCOM compliant program, to FTM a program that is not at all compliant.
Russ I do use AKA, I use it in a GEDCOM compliant way.