you can only load a single texture at a time, unless you do multitexturing (multiple textures layered on top of each other) so to be more precise one texture a "texture unit" normally your card can access like 4-16 textures at the same time, but not like per object, cause when you render a model that consists of multiple…
well if its an rts I assume the units are rather small ? think of average pixel area your unit will take on the screen and what your "targeted" screenres is (like 1200x1k..) it makes no sense that your textures are much bigger than the number of pixels they normally use on the screen. and about graphics, I wouldnt worry so…
Honestly. This is the kind of problem you'll want your programmer to solve. So in the event that someone comes screaming towards your direction yelling about how some model is using too many textures, you can point your finger at the programmer and say its his/her fault. Simple, really.
The reason to stick to large maps over multiple smaller ones comes from it being better digestible for the video cards. Both, Nvidia and ATI have enough documentation begging you to not ever use 4 small textures if you can fit it all in 1 large one. Ideally you'd merge 4 or 8 character skins into 1 4096 map... but then…