Squad/Platoon Leaders become HIgh Profile Targets(HPA). Killing HPA give more exp and may have a negative reprecussion for the squad and platoon.
Game already rewards real high profile targets with bonus XP for extreme menace, and higher XP for destroying tanks, MAX units, aircraft, etc. etc. Squad/Platoon Lead aren't necessarily "high profile" on the battlefield. They could be just another infantry unit, or whatever. Killing them doesn't take away their leadership ability at all. It's not like cutting the head off a snake. Also, if there were negative repercussions to the whole squad/platoon, the leaders are encouraged not to even enter battle at all. Making their job even more boring and limited to putting markers on map and/or giving orders in chat.
We already have bonuses for high priority targets. Those are typically called High Threat Kills, Extreme Menace Kills, and Killstreak Stops.
Killing the squad/platoon lead doesn't actually impede their ability to lead, though. Any rewards for killing them are purely arbitrary, and any penalties for dying as a SL/PL will just force them into a boring, conservative play style.
We could simply add squad/platoon leader to the list. The negative reprecussion does not have to be crazy; they can be small annoying things. I have never been in the military, so correct me if I am wrong, but shouldn't killing a squad/platoon leader be like chopping the head off a smaller snake?
The problem is that the quality of Planetside 2 squad/platoon leaders varies dramatically. Your average squad leader is barely above the average pubbie in skill level, situational awareness and general common sense. Killing them really has very very little impact in the grand scheme of things. Killing a competent squad/platoon lead puts them into the respawn screen, in front of a map, where they do their most important work anyway. This system would make a lot more sense if the ability to lead squads and platoons was restricted and had to be earned. However, anyone can start spam inviting people into a squad with little to no screening to prevent low skill players from leading them.
