2) No new enemies
I know what you’re thinking. How can you include the fact that you want to see something not be there. Well, my learned friend, I’m sure you’ve seen Ernst Lubitsch’s 1939 masterpiece Ninotchka. Perhaps you recall the scene where the main character goes to a café and asks the waiter for coffee without cream, to which the waiter replies “sorry, we’re out of cream. Can I bring you coffee without milk instead?” Not having something is part of the identity of what you do get, and if Halo were to hold back on giving us any new enemy types, the result would not be zero enemies.
Instead, we would have a more focused plot, with a greater depth and chance of expansion. There’s already the Flood, Covenant, Prometheans, Prophets, Forerunners, and plenty more splinter factions. Introducing a fresh threat, in terms of race, with every new game would simply lead to muddled, convoluted nonsense. More for the sake of more. I mean, look at Star Wars’ introduction of the Gungan, if you can bear to again.
Don’t get me wrong, I’m all for new characters, but a whole new bloodline just isn’t what the top of Halo 5‘s “to do” list should look like.