I've been watching this thread, and in Pro 2.6 I just used create locator for a street role with alt-names without any trouble. Not sure if I'm missing something in this post or not. Here in Utah we have both named streets and numbered streets. So we have S Main St or S 3305 E. However, each named street has a numeric equivalent. Sometimes, you never know what the address is going to come in as, the primary name or the numeric alternative. Here is a snapshot of my primary centerlines feature class as well as the alt names table:
If I enter 3565 S Mason Vista Way or 3565 S 7330 W, I get the same location.
Creating the alt names table is easy: I just select all those streets that have an Alpha name, and then export just those fields I need for the Numeric equivalent to a table. All of our streets have a UniqueID field so that is my join item:
That should just about do it....