Using uv is a habit.
When you typed that it made me think of something. I remember when a friend of mine from Europe told me that I abbreviated "welcome" funny. I would type "wlc bk." He said it read to him like "bathroom back." lol
Sorry back on topic....
I took a look at the props.txt files and noticed that the char export has 2 different texture mappings. One for 7 textures and one for 9 textures.
Here's the strange thing, the map props.txt file which shows 9 textures has the correct base maps, normal maps etc with the correct names. ActorX is reading from this one since in Max it shows roughly the same names listed on the multi-material, except Max shows 10 slots requesting the correct map names...
Now the one for 7 textures list maps that don't exist in the exported folders for that character (ie different texture names).
I think you're right, mappings at current are looking impossible. Or I should say, using the bms route, this is an issue. At least skeleton meshes, static meshes, and animations work.