I don't really know how Radianite works, and I'm not too deep in the VALORANT lore either. This is just my thoughts.

So, what if every agent in VALORANT had Radianite in them? Like Killjoy, Brimstone, Breach, etc.

Canonically, Radiants are the agents like Reyna, Jett, and Phoenix. But what if every human in the world had trace amounts of Radianite in them, making them all, to some degree, Radiants?

That would allow every stun and ability to work on anyone. And if all guns also use Radianite, this could also provide an explanation as to why they can slow down fire rate when an agent is stunned.

Why KAY/O's suppressor works:

It simply shuts down Radianite flow in an agent's body, sort of like stopping blood. It'll completely disable the abilities of a "true Radiant", while the "normies" will still get disabled, because their equipment, runs on Radianite.

Why enemy fires work on teammates:

So, enemy Phoenix's fire can damage the friendly Phoenix. I think this is because Radianite is different through all agents.

What if there's two types of Radianite? Pure, and harnessed. Radiants use harnesses Radianite, which is random and unpredictable. On the other hand, pure Radianite is what the Spike steals, and what all the diffusers use. This would explain why Brimstone mollies work on both teams, while Phoenix can survive his own flames. His Radianite is harnessed, while Brim's molies are pure.

Just some ideas! Feel free to inform me of anything I definitely missed.