Agent Richard07, since she would likely be a background character at most (if Abrams even considered the idea), the final illusion would probably be achieved via makeup, possibly something similar to the excellent appliances designed for an early David Tennent Doctor Who episode to depict a group of "cat" nuns (the "Sisters of Plenitude"). Unless she had a significant part, I can't imagine the production investing the resources to go the Gollum or Avatar route.
Some of the minor background aliens did appear to get the appropriate CGI treatment. That nurse/doc with the big eyes who delivered Kirk comes to mind, so I don't see why M'Ress couldn't be done the same way.
Background would suffice. It would be a nice little nod to fans, without being intrusive to those who've never heard of or seen TAS. Just to have her and Arex walking along would provide a nice little moment for oldies.
Agreed. I wouldn't have expected much else anyway.