Each team has 2 objectives, each regarding the other teams.
Alien Objectives:
-Destroy the Marine Satellite Uplink.
-Predator??
Marine Objectives:
-Kill the Hive Queen.
-Predator??
Predator Objectives:
-Destroy the Marine Satellite Uplink.
-Kill the Hive Queen.
The thing about this is that it could get messy. Lets take the predator, for example.
Predators are going around, trying to do their objective. The Aliens end up destroying the Marine Satellite Uplink, so they get instant credit(goal 1 of 2 achieved).
Yet Predators don't know its been destroyed, so they still have (goal 0 of 2 achieved). The predators would have to go to the location of the Satellite uplink, to get 'visual confirmation' that the Uplink has been destroyed. THEN they would get (goal 1 of 2 achieved).
And so on and so forth.
What would be better, however, is each race having DIFFERENT objectives from the other races. I'm keeping the above intact because it's still an idea.
Alien Objectives:
1-Incubate humans(like, 8?)(they have to go into the Terran sector and kill some neutral civilians, which in turn gives a neutral civilian in the Alien base. It takes maybe 2-5 minutes for a captured civilian to be Egged and killed)(make it so the predator shouldn't attack civilians)(Incubated Civilians can be force killed in the Alien base to "save" them.)
2-Entrap and kill Predators(6?). They have to lure predator's to a "set" random location(changes each time an ambush is tried, successful or not), which is where an alien ambush(with computer assistance) happens. This way, predator's won't know where the ambush happens, and can't outright avoid ambush).
3-Destroy the Predator Ship. When this happens, cut to cutscene, where the rest of the aliens are able to concentrate on the humans. GG Preds and Marines.
Marine Objectives:
1-Return power to the entire Facility, fix some wiring or something, and turn on the Satellite Uplink. (make the power generator somewhere far off enough so that it isn't too easy.)
2-Capture Predators(7?) in the name of science. Each time they kill a predator, they "acquire" it in their lab.(Captured Predators are rescuable by the Predators)
3-Capture 1 Hive Queen. When they kill it, cutscene ensues where they subdue the queen and turn the hive on the predators... GG Preds and Aliens.
Predator Objectives:
1-Destroy the Satellite Uplink and destroy computer terminals(3??).
2-Collect heads(25 total?).
3-Kill the Hive Queen. After killing the Queen, cut to cutscene where predators start cloaking and making their way to the Marine sector, where it's GG Marines and Aliens.
If it's an installation map, have the predator ship docked in a bay.
I think the above is all pretty balanced. Each races main Objective is their third one. the other ones are gravy. Make it so that the race gets a reward for accomplishing certain objectives.
Aliens:
-By incubating 8 humans, the aliens now have the ability to "become" Praetorian.
-Or, when they ambush 6 predators, they then get a regular "mini" patrol of computer controlled aliens attacking the Predator ship location.
Marines:
-when they fix the satellite uplink, they get regular "reinforcements" that help the Marines out.
-When they capture 7 predators, they've had enough time to analyze Cloaking technology, sort of, and are now able to "detect" cloaked predators for 10 seconds at a time or something.
Predators:
-When they destroy the satellite uplink... u come up with something for this -_-
-When they collect 25 heads, they gain shields(before 25 heads collected, their shields(not too much) are constantly set to 0. After 25 heads, they spawn with full shields and can recharge them with time.)
PS: My brain just died.
