Thanks for the feedback, everyone. I'm not at all concerned about rigging and animation at this point - that will all take place on a separate model altogether and the way the high poly model is set up likely won't have that much influence on how I do the retopo... but that's a headache for another day, in any event. From what I can tell, trying to rig, skin and animate the actual high poly mesh doesn't sound like a great idea, anyway.
The reason I'm feeling a little lost is simply that I have no real experience with "current gen" character creation; I've done a bit of modelling, I've done a bit of sculpting, but with the exception of a project for school using Maya and Mudbox (one I wasn't terribly happy with in the end anyway) I have never made a modern character model from start to finish. What I know about ZBrush is basically what carries over from Mudbox - the process of sculpting itself, and very little else. Half of the reason I took this on is precisely because I want to learn more about the typical workflow of creating a character primarily using ZBrush. So please do bear with me as I will probably do a fair amount of stupid mistakes along the way
tremor_209: Thanks a lot for that picture. I already have a fair amount of pictures saved but you can never have too much reference! This photo actually seems clearer than most of the ones I have, so it definitely helps.
Bleed: Scorpion looks great as always, but one detail just caught my eye, the way you can see "through" him when he extends his arm looks a bit odd. At first I thought there was literally a hole in the model or something, but I suppose it's just a side effect of how loosely the yellow vest sits over his torso. I will say though, judging from the angle of his arm, it doesn't seem like his shoulder would be that far back... maybe? I dunno, the more I look at it, the more confused I get. Whether it's "correct" or not, it may be something worth looking at.
Mortal Gojira: Tsung looks nice. I think parts of his face could be wrinklier still, but considering we never got a good close look at him (partly I'm sure because the makeup probably didn't hold up for extreme closeups) he certainly looks more than passable as far as likeness goes. His hair may be a challenge, but thankfully he doesn't move around a whole lot so it might not be a huge deal in the end.
calactyte: Thanks for the advice. I'll apply as much of it as I can.