Argus and Richard might make a decent team, given there's no obvious points of contention between them. Wouldn't be especially easy for them to kill each other if things get out of control.

At the same time, it might do good to partner Argus and Griffin, if nothing else so Griffin can get experience dealing with being partnered to someone via a fellow senior agent, rather than being stuck with a potentially inept rookie that might get on his nerves.

At the same time, thinking somewhat more pragmatically, despite the fact she could basically murder him without even trying Argus and Amaya somewhat cover each-other's inherent weaknesses. She can control water, which could be used to protect Argus from being snuffed out, while he is far more skilled in combat

Rost is a chill guy and can probably get on well with anyone that doesn't want to kill him for some reason. Possibly Mason once he's able to be an agent. Rost's Scrivening could be used to create seals to contain Shadow while still allowing MAson to use his powers, if he were to be given adequate time to study the precise nature of their abilities and begin developing countermeasures.