1. By default Q3D shares textures per object type (i.e. If you have a q3dmodel called object1 in construct, all object1 instances share the texture in gpu memory, but if you also have object2 with the same texture, its instatiate in memory. If you really need to share textures in gpu memory, q3dmaster has texture creation actions, and q3dmodel has a special "use texture from q3dmaster" action in advanced x stuff all the way at the bottom of the add action list.
2. You can use lightmaps with primary uvs to have two seperate "diffuse map" channels. You will definitely be able to do it with some colour replace shader when shaders are working properly, but itd require copying the existing phong/basic/lambert shaders first.
Thanks for reply! It's much more clear for me now. Can't wait for shaders and bone animations!