I think 3 may be unnecessary for a character. If I remember correctly most people use 2 1024 maps roughly. But if you need more detail, go for it but try not to use all 2048 maps. That seems a bit excessive. If you optimize your maps well your performance may not take a bad hit with 3 materials. All you can do is try out different options and see which works best.
Performance won't take a hit just from those draw calls. But if you are hitting a performance issue once everything is coming together that could be an area for optimizing. If it is possible use 1 texture sheet and material to reduce your draw call usage. However, if you need to have different characters share parts of a mesh, like a helmet or boots, then you have to seperate those onto their own sheet.
As for texture size you need to match it to whatever platform you are targeting. 1 set of 2048s is perfectly fine for current PC's. 2+ you can get away with depending on the scene or scope of the game.
Lead 3D Artist - Interceptor Entertainment