I haven't gotten a chance to read Shadow of Intent, but after reading the halopedia synopsis, I'd love to see ol' Half-Jaw and Shadow of Intent return in the next main installment in the series

Considering the predicament with The Created and Spartan teams Blue and Osiris ending up on Sanghelios at the conclusion of Halo 5, it seems likely that the Shadow of Intent would make a return to help fight Cortana.

I'd also love to see more of and hear more about Ranger Stolt, perhaps the coolest Unggoy in the entire franchise. This tough bastard not only earned the respect of his Elite comrades, but was given command over them. Hell, he even bests them in combat- not to mention he supposedly got the better of a Spartan II at some point. I'd love to see this guy in game.