Since Elites are confirmed not to be present in online gameplay, there’ll probably be a different gametype to take Invasion’s place. I, for one, would like to see a large-scale battle gametype. This is what it would include:
1)- Huge, open maps, possibly Forge-world size (maybe. Definitely really big though).
2)- No designated offense or defense: which one you are depends on how the battle is going.
3)- A base/territory system. Each side would start out with perhaps 3-4 bases: a primary, walled, heavily fortified base deep in their territory (which, by design, could not be captured except with inserting troops in dropships or breaking the gates with… something big), and 2-3 smaller frontline bases. Capturing these bases would yield you points; capturing them all would win the game. If there’s a time limit than whoever has more bases would win (it could be an ongoing play-till-you-win type deal, though, what with the “join-ingame” thing).
4)- Periodically you would be given resources. These would somehow be used to call down ordinances. Perhaps each base would include a couple vehicle- and weapon-drop spots; when a player gets to them, he chooses which vehicle (guass, rocket, or classic hog, Wraith or scorpion, etc. depending on size) or weapons (dropped in clusters: rockets, snipers, etc.) he wants called down. They would be limited by how many of the item is present in the field (only 1-2 tanks or 5 rocket-launchers per base controlled, for example)
5)- When one team captures all points, the other has to fall back to their main base. At this point (possibly) the battle is technically won; however, a timer will start and, if the defenders can keep the attackers from taking their base within that time, they will gain more rewards after the match. The attackers will gain access to dropships and Heavy Assault Platforms (like Scarabs). Defenders will have turrets, tanks, and AA guns set up on their walls: these can easily destroy dropships and HAPs. To gain access to the base, attackers must destroy several of these defenses in a coordinated attack and either destroy sections of the base’s wall with an HAP, or insert other Spartans with dropships (or both). Then you either plant a bomb (if you escape the base before detonation, you get a bonus) or capture a point. This will win the game.
I think this’d be a great way to introduce large-scale MP battles to the series. It would also allow for some new, more powerful weapons: sniper rifles that can actually “take the hat off an elite at 2,000 yards”, guided missile launchers, perhaps a Forerunner “guided sniper rifle”, etc. And who doesn’t want to drive a Scarab?