Aluminum frames should never be polished on the feed ramp. If you polish the frame you remove the anodizing, and the anodizing is what hardens the frame. A proper aluminum frame should be polished on the feed ramp before it gets anodized. If that's done and good mags are used, you should never have to worry about frame damage. Polish through the anodizing and it's something you'll need to worry about. If for some reason the feed ramp is damaged, the easiest fix is the ramped barrel. After that you can either weld up the frame, or you can have a steel feed ramp soldered in.
I have had aluminum frame 1911's for decades and I've never had any problem. My current S&W has nearly 10,000 rounds through it and the feed ramp shows no appreciable wear.
If someone is really worried about it, you could finish the frame in electro less nickel or NP3 and that would make the frame a rockwell hardness of between 45-60 which is harder than a steel frame and similar to the hardness of a fully heat treated 1911 slide.
