If you were wanting to make multiple Mongrel sub-archetypes, how would you go about it? I've started out by using the same basic stat block - all 2s, etc - and just changing the starting skill and the characteristics affected by The Beast Within . For instance, my Canid Mongrel starts with a rank in Perception and The Beast Within as described in the book, but my Felix Mongrel starts with a rank in Skulduggery and boosts to Agility and Cunning from The Beast Within instead.

Suggestions?

This is really a flavor thing per person. What I do when trying to think up how am I going to make up a new character is I'll go through all of the previous aliens in Star Wars. I then try to find other races that have similar flavors. If I'm trying to come up with something new, I try to find the closest thing to it, and then see what kind of weight FFG put into their version. As for switching out skills? I don't see a problem with just flip flopping skills in and out for bonuses, just try not to stack stuff too much. If you don't want to buy all of the books to get all of the alien races, ogg dude's character creation program is free and it has all of the aliens there, plus some home brewed ones that the community has made up.