I've seen that the miniatures come in pieces. Are the miniatures somewhat interchangeable for the generic units? Like in this picture...

Could I put the Duros' head (far left) onto the Commander Rebel's torso if I wanted?

Nobody knows just yet. The production models aren't even complete as of Gen Con.

Even if they aren't molded as separate parts, a head-swap is a very simple conversion with a hobby knife, glue, and maybe a tiny bit of green stuff if you want a really clean transition. This is quite doable for even a hobby novice.

9 minutes ago, Dr Lucky said:

Even if they aren't molded as separate parts, a head-swap is a very simple conversion with a hobby knife, glue, and maybe a tiny bit of green stuff if you want a really clean transition. This is quite doable for even a hobby novice.

I think he means, official rules wise. For example in X-wing is tournament legal to paint your minis but not modify its "shape or size". I hope they pick some reasonable rule, I actually like GW ruling for this which mainly is you can customize if you use parts from the GW line (plus some size and base rules) which still encourages originality while keeping 3rd party manufacturers at bay.

They will not come on a sprue, so it will depend on the heads coming attached to the body or not from the mold.

I would imagine rule wise, modded minis will be fine. I dont think FFG would be smart to eliminate the Hobby community from Legion all together. The Hobby community will be the bulk of Legions sales, just as it is for the vast majority of mini games.

That shouldn't be an issue here. Being a more traditional war game, it's likely to be a bit more relaxed on things like headswaps.

Rebel Troopers are rebel troopers after all, regardless of species!

Do not play with a person who states that one model's head is incorrect and therefore against 'the rules'.

I think this game needs people to remember a very important saying;

Rules are for the obedience of fools and the guidance of wise men

I think as long as the unit commander is clearly distinct, it shouldn't matter at all. I personally want enough Duros to field only them haha. Humans are lame.

I hope so, especially when playing around with race. I almost always play Imperial in IA and X-wing, but if I can get an army that is mostly or entirely non-human, I'll play that in a heartbeat. I know this won't happen without some custom modification or optional bits or whatever, out-of-the-box both sides will be mostly human for sure.

Never really liked how human-centric the Rebellion seemed to be, doesn't fit with the lore. Makes sense from a movie-making standpoint of course, but in-universe it has never sat right with me.

head swap shouldn't matter at all

There are some points in the Runewars tournament rules: https://images-cdn.fantasyflightgames.com/filer_public/ff/d2/ffd221c7-808e-4926-b09c-2268cfc4882c/rwm_tournament_regulations_v10.pdf

But I think it's posssible, that there will come other rules for Legion cause of the licence.