I can see what you mean, actually, OddHunter. Perhaps a middle-ground would be best, so as not to humanise too much; maybe they could occasionally engage each other in the same kind of chit-chat as when we see them conversing just as Abe enters the Stockyards. It's unintelligible and emotionless, much like the Metropolice radio chatter in the start of HL2... which makes me think.
In the first game, ALL of the industrialists spoke in low, obscure voices, and as far as I could work out, were not meant to be fully understood by the player. Kind of makes them seem much more merciless. I think as long as any Slig chatter was done like this, and the aforementioned cutscene, it could breathe a little more life into the environments while not breaking character.
Just don't make them speak with the same jive mannerisms as in Munch... I always thought that was awful.
Just two small things I thought of while writing this post;
1) I hope the Sligs still spam BS and S'Mo BS when they're about to beat the slaves silly. To me it's highly iconic.
2) Can't remember if we've had word on this, but I hope the Sligs use the visor mask from Oddysee. Looks way cooler and more emotionless.