PLEASE let's not do the Traviss debate here. Right, wrong, petulant, whatever, just leave the dead horse alone to decompose.
mandalorian species
You can't really make a Mandalorian "species" any more than you can make a "Rebel" or "Imperial" or "Black Sun" species. Being a Mandalorian marks you as a member of a culture, so that would be more of a roleplaying/Obligation/Motivation aspect of your character than any mechanical benefits; you would have to build your character in such a way as to represent how they've spent a lifetime of training and fighting (Bounty Hunter/Hired Gun/etc).
Classes and Specializations aren't just the role your character settles into on the Fringe, they represent the path they've taken to get where they are now. If your character starts off with two points in Ranged Light it's not due to their species, but the fact that they trained as a part of their chosen career.
I agree with you completely. Just to pick at this idea some, it sounds like if you were to codify a mandalorian at all, it would be a career or specialization. Granted there already a few careers/specs in EotE and AoR that could work in stead of building your own, but that's definitely a direction a GM could take if they weren't satisfied with some of the more applicable substitute specs out there.
I think its possible (and justifiable) to make a mandalorian human variant, particularly now that FFG has presented another human variant species in the Corellian Human.
Ah well. This seems like yet another dead horse.
If I were to homebrew a Mandalorian variant "template," I might allow a single rank of Coercion at character creation for free in exchange for some other benefit, like a humans' non-career skills or another species' talent. Or 5 XP or whatever.
I suppose it might be easier to make the call once Suns of Fortune hits the shelves.
Well, there might be some talk of the Mandos in the upcoming Dangerous Covenants source book (just announced). Since they're primarily a warrior-centric culture, it'd be as good a place as any to toss out suggestions (or rules even) for playing Mandalorians.