Aluminum being one of the most abundant materials on Earth would be great for coins but the counterfieters would have a field day. Stainless Steel is the way to go. All coins should be made of Stainless Steel. A high grade so they would be non magnetic. No rusting. No toning. Little wear. No mixing of metals once made always would be the same for all coins.
The problem with this is that they would get very damaged very quickly, so huge amounts of them would have to be made.