Its gonna be pretty to have this function having watermark on photo just like having a date and time on photo, i think is possible to have names on photo
a watermark with simple fonts and color
Usually things done with a simple click of a mouse in any post processing application dont make it as feature requests...
For copyright and marketing purposes. this gonna be a great function doing it without a PC in post production
If you can make up a proper use case why this one cannot wait to pp you may find support. And "gonna be great" doesn't qualify as use case.
Camera is already adding copyright info as metadata for RAW shots if properly setup...
But pictures can be edit in photo editor and change the copyright meta info..
Generally, functions that exist in PP are not implemented in ML.
As Walter suggests, you can make a convincing use case.