I can imagine it getting out of hand pretty fast, but I think it might be worth a try. So like, do you think it would be a bad thing if implemented? What's the worst that could happen - besides the best crucible weapon becoming even more effective... even then, the other weapons could also be powerhouses since you can apply the same perks. Come to think of it, this would go horribly wrong with Rocket Launchers as everyone would apply Cluster Bombs.

I think maybe they have a tier system and you can only have so many of each tier on each weapon