Sorting defectively needs an overall and full scriptability. There's already feature requests for that.
But this one would be an option to those.
The idea is to be able to script the sorting and tell filemaker to treat that field, as if it were from another field type.
So, with that sort as field type feature, we would be able to sort a text field as if it were a number field.
Or a text field as if it were a datte, time, timestamp.
So, we could at runtime have the sorting method that suits us best, regardless of the actual field type.
What for ? Plenty of things surely. Decoupling. But here's my need :
Well, as text field format can accommodate anything, you can use some text fields to receive data from a variety of sources, no matter the original field type (except containers of course). So you can create a Table / Layout to manipulate, transform data from any source, and/or you can create a Table / Layout that would be a universal display / manipulation tool for any data. But now, the only thing that misses is the correct sorting order.
So rather that having several list views to display data from different tables, you could have one layout that would fit plenty of data displays (a script would populate the universal receiving table, and you'd work on this visualisation. That's good enough for a lot of stuff).
P.S : Yes I'm willing to take a performance hit for this. I know field types are here for a reason.