Not to chase you away from this forum (and I for one hope you post your build here) but I would check out what the fellows are doing in the MetalWorking forums. Some very talented guys who probably have more ideas of what is needed for soft metals milling.

Here's one of the latest builds to inspire you (though it's a budget breaker!)
http://www.cnczone.com/forums/vertic...ml#post1196771