I don't know Gmax, like, at all, but if the material system is anything like 3ds Max, you'll end up using a multi-sub map.
I recently decided to change my texturing workflow, actually, so I'll tell you in the interest of you learning from my woes. Essentially, what I do is work in discreet stages. Model, Unwrap, Texture. I'll model the object, (with some idea on how it's going to be unwrapped), and then I'll unwrap it in the best way I can. Once I've unwrapped the model, the design itself will tell me how many textures the thing is going to need. When I unwrap, I bear in mind what is going to be needed as far as texture design goes. I'll try to keep different sections together on the same map, or things that have the same look and feel (ie: running lights or greebles) on one map. I'll then detach the model into discreet parts according to which map is where. After that I'll build the textures and then assign the textures to the discreet parts. I will then run a script that generates a single mult-sub map that includes all the materials of the different parts, and then attach all the objects together, leaving me with the most efficient multi-sub map one could ask for, without needing to toy with material IDs which can pull me out of the flow.