When you say SP/MP dmgs, is this referring to the JA+ system, as I don't know what "pure base" uses. Also, having a few custom maps in the server roation would be nice, or atleast available to vote on on the server
The uv map is completely different for those models, so copying the textures over would look like a mess on the rebel model. You'd need to edit the rebel's textures, and copy the various parts you want from the arc trooper onto it. I made a tutorial here on how to make/edit a skin and get it ingame if that helps you at all, but there are also plenty of others out there on the topic
Are you wanting to get a downloaded skin ingame, or copy over the textures of it onto another model, as it seems like you're asking two things here? Wonko means that putting more information in the title. Reason being is lots of people ask for help, so stating the general topic in the title would probably help more people give you an answer.