Earlier quoted context omitted.
Perhaps you could help by inventing a written version of ASL, since one doesn't currently exist. [EDIT: I was wrong, sorry, see my response below.] Seems like that would be a prerequisite for a model based on written language. And of course if you could also create an entire corpus of training material in your written ASL?
It is called SignWriting for all you multiple naysayers. https://en.m.wikipedia.org/wiki/SignWriting
I suspect Meta/Facebook doesn't have a lot of content to work off of. I've only been able to find community-generated examples of SignWriting on the official website[1], and none of those seem to be using Unicode characters. MMS is an audio-to-text tool, so it seems unlikely that it can be trivially expanded to take in visual data (pictures of text or video of ASL being performed).
I suspect the process of turning viewed ASL into SignWriting text will be very difficult to automate. I would not be surprised if such a project would either use a different textual encoding or directly translate out to English (which also sounds terribly hard, but these LLM advances recently have surprised me).