Add a new set of upgrades unique to that map that are defensive emplacement upgrades.

These would be given every 5 ways and would add permanent things to the map granted the flood might add something to counter them later.

Example of ideas.

Engineers
info: spawns two engineers at the base who will repair any vehicles that get close (if possible.) and heal any allies as well. (can be picked once.)

Barricades: places H1 shield barriers around the base. (can be picked once)

Minefield: a phantom flies over and drops mines over the flood side of the map. (can be taken inifnite times)

Wave spawn: grunts each wave 2 grunt minors will spawn.(can be taken twice.)
wave spawn: elite, each wave one elite minor will spawn. (can be taken twice)

Advanced barricades (requires barricades)
info: blocks off the side flood path with a one way shield and generator (like seen in the campaign only blocks organic as well, can shoot through.)

Gate barricade
info: adds a shield to the gate that players and allies can move through but flood can not.

Mine crate: adds a crate of mines
turret crate: adds a crate that has 2 turrets respawns every 3 waves.



SPIKE TURRETS (requires engineers)
info: places a spike turret aimed at the main vehicle entry good against infantry.
note: has 4 levels the second level adds another spike turret to the battlements, the third upgrades the entry one with a fuel rod, the 4th adds a anti infantry plasma to the battlements one.

Sniper tower (requires engineers)
info: spawns a sniper tower on your half of the map, by default two jackal snipers will move to man it.


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Phantom gunship
info: calls in a phantom gunship that will rain down plasma and fuel rod fire on the field includes two side door gunners, three heavy plasma turrets (like H2 phantoms), and 4 grunts with fuel rods siting on the sides.

this phantom will remain in the fight for 5 waves or until it is shot down by rocket flood.