What if:
When you build a weapon, its level is set to what you forge level was when you build it.
But you can add just as many forge point as your forgelevel allows it, without using a BP, but you cannot go any higher than what the level allows on which the BP was build.
Each forge point could cost... 2000 gold?
The result i think is that you feel like you are actually making progress on your chosen weapon, rather than constantly waiting.
And you will still have to farm for BP if you want the weapon to have higher stats, so they should remain as they are, even their current gold price would make sense with this, unlike as it is atm.
Also, your current BP drop system is still jank.
You try to encourage teamwork and team comps, but you HAVE to play as the raider you want the BP for, encouraging ingoring team comps for just a chance at that BP.
Often being the reason you have a terrible team comp and match, as most people REALLY want that BP.