you can restrict killstreaks in in the tdm.cfg file (and I assume other gamemode specific cfg files)
using the following
restrict_item "killstreak_spyplane" // UAV
restrict_item "killstreak_rcbomb" // RC-XD
restrict_item "killstreak_missile_drone" // Hunter Killer
restrict_item "killstreak_supply_drop" // Care Package
restrict_item "killstreak_counteruav" // Counter-UAV
restrict_item "killstreak_microwave_turret" // Guardian
restrict_item "killstreak_remote_missile" // Hellstorm Missile
restrict_item "killstreak_planemortar" // Lightning Strike
restrict_item "killstreak_auto_turret" // Sentry Gun
restrict_item "killstreak_minigun" // Death Machine
restrict_item "killstreak_m32" // War Machine
restrict_item "killstreak_qrdrone" // Dragonfire
restrict_item "killstreak_ai_tank_drop" // A.G.R.
restrict_item "killstreak_helicopter_comlink" // Stealth Chopper
restrict_item "killstreak_spyplane_direction" // Orbital VSAT
restrict_item "killstreak_helicopter_guard" // Escort Drone
restrict_item "killstreak_emp" // EMP Systems
restrict_item "killstreak_straferun" // Warthog
restrict_item "killstreak_remote_mortar" // Lodestar
restrict_item "killstreak_helicopter_player_gunner" // VTOL Warship
restrict_item "killstreak_dogs" // K9 Unit
restrict_item "killstreak_missile_swarm" // Swarm
this will just disable the specified killstreak. I am currently not aware of a way to replace a killstreak with a different killstreak. I'm also not sure if a restricted killstreak can still come out of a care package
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