Hmm, This idea has a positive side, but also a negative one
1. Yes, the idea is nice to see, all those shiny weapons, and it would sure be possible. The Zircon Sigil would be the best example. It should be (I'm not a dev, please don't kill me for this) quite simple to change the item to look like +16, 17 etcetera, and maybe add a few hours to the duration. You can put those in the monkey coin shop for like 100 MC per 'sigil'. Like I said I'm not a dev, but I assume that the item should be easily editable.
2. I don't think many people will care about the color of their weapon once it's live. My personal opinion is that I would use it for some days, and then forget about it. That's because it's an item that needs to be 'activated', if you go for the Zircon Sigil. Again, this is my personal opinion.
In a nutshell: Yes, the idea would work, but it needs to be easily obtainable, since it's a 'fashion' type.
Regards,
Ikke.