Look, I don't want to be mean or anything, but basically all I'm hearing from this post is "I want a bigger gat" which doesn't add like... anything to the game. Gats are meant for armor stripping and the current one does it just fine, there's no reason from a medium sized one.
There's also some thread somewhere which basically determined that it'd be a terrible idea to have an upgraded gat as it is, I'm too lazy to go find it though.