I like the idea of the deep multi-layered onion approach to Skinnies.
I'd also hope that given their diversity that certain Skinnie groups would be in league with less than common alien species that may or may not warrant an entire army list of their own. So while some Skinnies may use slaves, others might have willing allies from more unique species. I'm thinking single units or individual aliens as scouts, advisors, engineers, mercenaries, bounty hunters, psychics, etc. Then if any single type catches on with the fan base, Mongoose will be able to expand upon that particular test case alien with more material later on. Besides the quality issues with the slave unit figures, I think an opportunity was missed to more thoroughly describe what worlds the slaves came from and the different species, perhaps giving some special talents or abilities.