This is a great idea! The original post and the point made by you. However there is a few ideas that could be added to make this subject a bit better. The idea of perma-unlocked attachments is a great one but could become completely over powered. So here is a thought, why not consider only certain attachments that could be perma-unlocked? A choice of a set of 10 possibly? The limit allows for customization for everyone that you like and want, but restricts it enough so you don't push it to round 105 using one gun that is completely over kill (granted the bullet count to kill a zombie on this round would be terrible but non the less just to prove a point). I don't believe it should be set by 3-arch but they should decide the limit of attachments you can unlock permanently. Honestly this could revolutionize the strategies and ways people play solo. Also yes it should stay solo and have its own separate leader board... possibly. That could kind of show you how people do with their own setup. If a separate leader board could be made showing the guns that had their own custom twist by players and how well they did it would be a nice addition to the community .