Unpopular opinion it would seem, but I gave this a 3/5. The system is moderately complicated and took a couple of reads to really start to understand it. In fact, there are still parts that I don't understand. What's the point of having subtypes? They count as same names as other features that also have that subtype. There are no duplicated subtypes on the list of upgrades. Why not just have their names then that would already limit it to one per weapon? Also, there are numerous grammatical errors which further complicate understanding this system.
I feel what makes this a bestseller is that there just isn't really anything else on here that goes to the lengths that this does for scaleable weapons. That being said, there are some interesting ideas here and, like many others have said, with some tweaking this could be a really interesting addition to the game.
[3 of 5 Stars!]