Regarding the 'z's in a lot of the species' names, around the early 2000's (when I assume the first concepts for SW were created) a lot of people did this. They though for some reason it was cool.
I'm willing to put the overuse of the letter z down to being a cultural reference/trend at the time the game was created. Though admittedly, this 'trend' was long gone by 2005, so I guess they could have changed things before release.
I would not expect this to be done now though! In no way is it relevant these days. I think I might explode if Abe HD features 'mudokonz', 'sligz' or even worse... 'birdz'
All in all, I haven't played Munch (looking forward to the HD version). Stranger was on the whole a very good game. There was something about the atmosphere though, which seemed to straddle a line between Oddworld and something else. The beginning hunting Outlaws didn't feel that much like Oddworld to me, but the end was great. The buildings and structures got far more imposing and the tone became a little darker and less goofy.