I think that theoretically it's possible, it depends how deep you have to dig into the material with the milling tool. I mean... if the shape is rich of vertical "walls" then you will crash your thin tool (let's say a 2mm diameter milling bit). So you will need a more rigid milling tool (let's say 5 or 6mm diameter). But in this way you will loose the ability to produce fine details.
Honestly I'm not an expert of milling deeply into aluminum, so I hope that somebody with more knowledge could answer you.
Anyway I think that the software in this case has great importance. I mean... I think that you need a "smart" CAM software able to produce a step-by-step process. The first milling step should be executed with a big diameter tool, second step with a smaller one and so on. Refining details on the way.
I cannot imagine how much long all the operation could be long, minimum one day (24h) for sure. In any case you need a spindle with the highest torque possible. Maybe the Stepcraft 500watt it's enough, but I'm not sure of this.