I am going to make some story lines up that could be interesting..then other people can do it if you'd like.

K..

Well..you start out at Earth I'm guessing? Well..you save Earth, defeating the covenant, killing most, and chasing the rest out. MC gets a ride back into the new space station place, and they find alien signals over some radiar or something. They chase it and find a new level, and it's not covenant, nor the flood, this is where the new characters come in. MC and the marines can't defeat these guys...so something drastic happens. MC has to retreat, he can't kill all of them because his marines are now all dead. He goes back up to the space station..and the new captian keys guy and a bunch of other people have to think. Finally, they come up with an idea to make more MC's (forget what they're called..even though I have the book right next to me ) like there was in teh book. MC and 50 other super humans go down and defeat the other species, while the other things from the other species leave..and you go home, back to earth, and have a huge celebration with Earth people, you remove your helment and are now known as a hero.

I think it's a good idea, but it could end the series.

Anyway..whatca think?