This is going to be quite a longshot of an idea, but I think if I explain it well enough a lot of people can back me up on it.
Basically, I want Halo 5, or any future mainline Halo games, to have the Scan Visor feature from Metroid Prime. In the Metroid Prime games, Scan Visor worked by hitting a button to switch visor modes. In Scan mode, little holographic icons could be found hidden amongst the level you were in, usually on enemies, bodies, architectural pieces of significant importance, statues, computer terminals, etc. When you found one and walked up to it you could hold down a button to scan the icon and special information would be displayed in the form of text. This text would then be cataloged in a log book you could refer back to at any time you please. This information could be anything from enemy biology, weaknesses and strengths, history on a certain piece of junk, lore tidbits, whatever, just little bits of goodies!
I think this feature would be an extremely welcome feature to the Halo campaign for many reasons. It could act as a bonus little collect-a-thon feature alongside skull hunting and terminals, and it could enrich the single player experience by multiplying the replayability factor by threefold! What do you guys think?