I personally just want a higher player cap and vehicle count.
I'm not really into classes and whatnot. I mean I suppose they could be done in a way that works but from what I've seen of H5, not so much. There's no real reason for it. Spawning from a drop pod would be cool though imo (depending on the size).
Booshka's explanation is right on point as well.
Infantry combat in Halo is a whole other level of fun than other games.
Invasion should be what you're talking about and BTB should be what Booshka said. Boom, game types for both kinds of people.