I agree about him playing a new character, unless he's an avid fan of Swan Song (I know he's mentioned watching Rollplay before, but I wouldn't guess he'd be a "chronic fan" like the rest of us). I do wonder what role he'd be playing, though... Swan Song always had its awkward crew members.
I'm guessing Rajani is likely to make a comeback, since she was something of a big deal as far as supporting characters behind Pi.
My money is on Geoff playing Sicarian.
I hope we see Luminary stuff, though I'd imagine Pi is gonna be a bigger focus for the live show, so there might not be a whole lot of room for Higgins' "side-plot".
Higgs was my favorite character. It was JP playing to his strengths and doing it with consistent hilarity, as well as surprisingly subtle depth. Many of my favorite dramatic moments are when Higgs has to be a hero, and no one ever really acknowledges him (one of my fave all-time episodes was when they had to crash-land and Higgs had to stay awake while everyone was in induced comas).
In some ways, Higgs is a more emotionally-interesting character than a lot of your other classic space rogues, at least for me. He's not a wisecracking badass or a rogue with a heart of gold - no, Higgs is a straight-up selfish asshole and a nigh-comical failure of a human being that stumbles into success in the most fucked-up ways possible, but he still values the people and experiences around him even though he might be hard-pressed to admit it. And he'll risk his life for those people and no one will notice.