Many people thought the same way when it came out, but the proportions are nothing new... Many duty guns have a full size grip with a ~4" barrel. 1911 Commander, HK P30, HK VP9, etc.I was the same way, longer grip + shorter barrel seemed kinda opposite what I normally would have gone for, but it shoots well and feels good in the grip!
This is what I have done with my G19. I just label my Gen 5 for use with other guns.Or just buy gen 3 or gen 4 G17 mags