Currently, you are only given grenades when you respawn. This is however, unrewarding for players who stay alive for being good. We can easily solve this by giving them grenades after enough kills:
+1 Explosive Grenade per 2 kills.
+1 Port Nade per 3 kills.
+1 Shield Nade per 5 kills.
You can only get them in maps where they're enabled in the first place.
Also, some trigger actions:
Set disabling of grenade refilling for grenade type A.
Set enabling of grenade refilling for grenade type A.
Set grenade refilling multiplier to value A for grenade type B.
Set grenade refilling kill requirement to value A for grenade type B.