Okay, so I've played a few games with McCabe, and have really enjoyed him. I won't profess to being an expert (nobody is at this point!) but I do feel like I've got a decent handle on how he plays.
Basically, McCabe seems to be a very fast and versatile Master - able to pull allies along, buff them with upgrades, disrupt enemies with his netgun and generally just help out wherever he's needed. His crew tends toward mobility, card draw and gaining the focused condition like there's no tomorrow. The latter is great for boosting attacks and avoiding damage, but beyond that their killing power and resiliance is pretty average.
So, onto McCabe's crew;
Ruffians (formerly Wastrels) are there to push your bigger models around, draw cards with looted supplies, plink off damage with their focused shooting and drop scheme markers as needed. Basically, they're great because they're cheap and versatile, so I feel it's always worth including at least 1-2 in your crews.
Hucksters are your scheme runners. and they're GREAT at this role. Secret Passage lets them teleport across the board, before dropping ridiculous numbers of scheme markers with False Claim. Combine with the Trained Ninja Upgrade, and he can do this from turn 1 anywhere on the board! Obviously there's no model currently available for these guys, but they're absolutely worth finding a proxy for while you wait for an official release.
Sidir is the Crew's only in-keyword killing machine but oh man, he's worth it. Between his Machine Gun and stripping cover with his Blown Apart marker, he's quite capable of tearing holes into anyone who gets close enough. Plus he can strip Armor and Shielded, allowing you to deal with models that might otherwise prove near-impossible to kill. In summary, Sidir is as close to mandatory for McCabe's crew as you can get.
Luna and Desper Laraux I don't really want to talk about - The former I've only really used to drop scrap and die (for a corpse) and the latter I've yet to put on the table.
So that covers the core of McCabe's crew. Beyond that, there's two Versatile models I'd absolutely recommend, and those would be Samurai and Tanuki
Samurai are great at almost everything. They're very tough with Armor +2 and healing, and are brutal both at range and up close (he even ignores armor in melee!). Their main weakness is that they're slow, but that's easilly fixed with a Ruffian or McCabe to push them along. But what seals the deal for Samurai, is that they're minions. That means McCabe can give them artefacts, with all the benefits that comes with. Basically if you need some muscle for your crew, Samurai are your answer.
Tanuki are mainly there to plug the remaining two holes in your crew - condition removal and healing. He does other stuff, but you don't care about that. You care about Condition removal and Healing.
In regards to generating corpse and scrap markers, this isn't something I've gone too deeply into with my games. Luna and the odd dead Ruffian has usually been enough for my card draw/artifact needs but again - I've only played a few games so maybe I've just lucked out. In any case another potential source of scrap is the trigger on the Hucketer's False Claim, so that might be worth pursuing. I've heard people talk about an Obsidian Oni or Obsidian Statue. Both of those might work too, though I've not looked too deeply into how well they'd work beyond just generating scrap.
That's it for now. If you want the TL:DR version here it is in point form;
1. Proxy Hucksters
2. You definitely want to buy some Samurai and Tanuki.
3. The core crew might generate enough Scrap/Corpses for your needs, but I can't be sure yet.