It would be very interesting to introduce high-level skills and responsibilities for veteran players to deepen the late-game progression.
For example, once a player reaches a certain high rank, they could unlock or be transitioned into 'Hardcore/Friendly Fire' mechanics. To protect the onboarding experience, newbies shouldn't have team killing enabled, this prevents accidental griefing and learning-curve frustration. Instead, only experienced players would play with this added layer of realism and tactical penalty.
By tying friendly fire to high-level lobbies or specific veteran roles (like a Team Commander), it adds a massive layer of skill, communication, and responsibility. I'll leave the exact balancing and penalty systems (like rank demotion, temporary bans, or credit deductions for team killers) to the dev team, but adding this progression would immensely elevate the competitive endgame.