Edit: Added suggested changes

So people believe that Stim Beacon is the worst part of Brimstone abilities and sometimes don't even buy it. Here's my suggestion for a change. The controller class is supposed to be able to divide up the battle field and "slice up territory to set there team up for success". For the controller agents this is by blocking line of site mostly and making areas dangerous for the enemy to go into with molleys. Brimstone character is about "on the ground commander" so what shows commanding than standing your ground after getting into place.

Stim Beacon before:

2 charges / 100 credits per charge / 12s (3.5seconds after leaving area)

Instantly toss a stim beacon in front of Brimstone. Upon landing, the stim beacon will create a field that grants allies RapidFire. RapidFire increases fire rate, reload speed, weapon swap speed, and recoil recovery by 15%.

Stim Beacon after:

1 charge / 200-300 credits / 8s

Equip a stim beacon. Fire to toss a stim beacon in front of Brimstone with 100 health. Upon landing, the stim beacon will create a field that grants allies within RapidFire and Stalwart. RapidFire increases fire rate, reload speed, weapon swap speed, and recoil recovery by 15%.

Stalwart will give immunity to flinching, flashes, displacements, disorientation, tagging, slows, any kind of crowd control effects.

To readjust power it will also place a blinker on the map (like Sova arrow) and have a larger sound effect so enemies know it's happening. Moreover you only gain the effect while standing in the area, it doesn't persist for awhile after leaving. Price would increase to like 200 or 300.

I think this fits into the controller playstyle because the player creates a space where their team will have an advantage and be stronger in the fight. The enemy will know this location too and will have to think whether or not to contest it while it's up. I think the idea is similar to an operator player. You are conscious around the enemy OP player and play around them because it's a powerful gun that will screw you over if you don't respect it. For a few seconds Brimstone will create a small space on the map for him and allies where the enemy should try to respect it. It also reinforces the idea that he is an anchor on a site and helps differentiate himself from Omen.