The short answer is "certainly" with the qualification of the right machine design, the right cutting tools, feeds, speeds, etc.
There are a great many variables that will determine the prcaticality such as the size of the machine (mass of the moving parts), type of drive (inefficient threaded rod vs. efficient ballscrews), Type of aluminum to be cut (many different grades and tempers), etc.
The machine that I've been building is currently using threaded rod until I am satisfied with it and convert it to ACME screws. I'm using 80 oz steppers with the HobbyCNC chopper board. The approximate work area is 2' x 2' x 12" and I have a RotoZip RZ1 as a spindle.
I haven't tried aluminum yet since I'm still finishing construction, but I have done test cuts in MDF that leave me with little doubt that with a good 1/4" end mill and a speed control to slow the spindle down to a suitable speed this machine could reasonably cut aluminum with moderate depth passes.
The 200 oz steppers should give you plenty of strength as long as the rest of your machine design is appropriate.