I could look into this, but it would probably mean having less passive slots to start with the potential to have more then three towards the end for balance reasons.
I just had a cool idea for a mechanic: I like how there are so many weapons but it always ends up feeling like one isn't enough,, it would be cool if the two weapons (at least the silver ones) were both active for more build crafting
One weapon per slot is enough if you get good ;) I thought about doing some crafting and weapon upgrading stuff at one point but it's a very time expensive thing to add. If I make enough money to put more time into this in the future I'll upgrade some of those systems for sure.