There is only this one problem with your analysis here. In A16 you get all your gun parts together pretty quicky, non matter how ♥♥♥♥ty the quality it has. In A17 it is not as easy to get a purple gun that can fit in 5 parts. So if someone are to follow your approach here he will have no guns for use until mid/late game.
P.S: I can go with either system. I think both system are interesting and fun. May be the two system can be combined in the future. Make it so that guns have 5 parts(quality, which affect damage, durability and mod slot), and 5 slots for functional mods (scope, red dot, handling etc). More parts that leads to perfection surly helps to extend the life of end game.