So, I was thinking a small and simple, but significant change could be made to big ticket guns such as the Bar, Pbp, Minigun, and various legendary tier weapons(PK/Spar Weapons). The central idea revolves around making the the weapon harder to maintain and by that I mean repairing/upgrading.
What we could do is simply add a rare mineral(such as gold, rubies, diamonds, emerald, maaaaybe silver for the mediocre tier weapons) to the list of minerals required to upgrade/repair weapons. The higher tier the weapon, the rarer the mineral required. For instance:
Bar, PBP, and Minigun would now require 2 gold in addition to the regular minerals to upgrade.
The PK/Spar weapons would now require 1 diamond(or emerald/ruby/sapphire) to upgrade.
Mediocre guns that are still pretty good would now require like 1 silver or something simple.
Something along these lines but doesn't have to be this exactly. The main focus is making these weapons harder to maintain, since they are rather easy to obtain.
I am open to feedback and please feel free to share any ideas you have to improve this idea!