After reading a bit about Randall from Halopedia, it seems he at least would've made just fine character. If there had been time to develop him a bit more in Nightfall. Not atypical issue with TV/film though.
At least he wasn't as bad as the ONI guys, never even caught their names. Oh, well, whatever.
Conceptually, returning to a Halo's fragment is pretty neat, certainly makes for nice landscapes, even if they had to make it burnt all over.
A shame about not using the Flood, a lekgolo variation is a bit... exotic, for anyone not delved into Halo's lore more deeply. Not to mention, doesn't really match what we see elsewhere, where lekgolo colonies like Hunters can die from losing some of their numbers. (Yes yes, they're Forerunner modified but that doesn't really help things any, just makes them even more complicated.)
Would like to see a live action Halo set during the Covie war, middle years. You know, 2535-2540 or so. That time period hasn't really been covered. Perhaps a good Covie point of view as well, show how things are at High Charity or some other colony of theirs.