As it is no one has a use for the spark trinkets after comparing them to weapon modules. Second, the spark trinkets arent very strong at all, they give very minor bonuses. Also given the shadow key update it seems you want extra money :P
1. Make two extra trinket slots for weapon modules only (and possibly heart pendants), and keep the current slots for the other type of weaker trinkets, the prices at boost shouldnt increase since you are doubling the cost already, but whatever.
2. Just like armors get accessories, make the weapon slot modules use an accessory slot for weapons instead of a trinket slot. Using the same mechanic, bound to the weapon and lost if removed. It brings money to you since everyone will rush to spend energy on these modules for their every weapon. instead of getting up to two of each and never buy again. I feel this would have been better than releasing shadow keys to cover costs.
I'm gonna say this right now before this goes any further...... We are REALLY close to turning the gear system into a major stack fest. The function your suggesting is already filled by UVs, but yours has an insane additional cost attached to it with slotted weapons.
The game already has a +6 hard cap for any particular bonus. And at the rate things are going, we're gonna end up having Max bonus in at least 4 different areas per character on a full load out. In PvE its one thing, but Lockdown adds a pressing need to balance weapons out so they don't create heavy separation between players who can only afford 1 set of armor, and players who can dump tons of CE into owning every thing in the game.