No Star you are missing the point, no Tuaparangs being good guys, let me ask you, do you want to play as something like Blados or Chalis or something like Saturos or Menardi?
It's not the specific species that matters, it's the inner conflict that one would have from being forced to fight against their own kind. It could be a story of a person who disagrees with what their country's fighting for, and decides to leave for a better place, and forced to fight. Or, a story of someone who hates the world, and just wants to get rid of the worst first. If I make sense. The point is inner conflict, not outward appearances.
The rest of what you said is kinda really stupid sounding, so I'm not gonna bother with going through it.
So you're saying you like to see Blados and Chalis more than you'd like to see Saturos and Menardi?
You know that's the same as saying you want to see Tatanga instead of Bowser.
My point is Golden Sun needs a Saturos like character, or else the villians look really stupid, like Blados and Chalis, since Alex is designed as more of a manipulative type bad guy, in the original Golden Sun, Saturos took the lead role of playing the antagonist, Alex is the main bad guy, but Saturos was his right hand man.
Saturos left a legacy in Golden Sun, which is why according to fans, he's the best antagonist ever, so if he achieved this, why not make a new Saturos, a new Proxian villain to fill in the shoes of Saturos?
As for the good Proxian it would basically be similar to Mia's story with Alex, I'd like to see a new Menardi used here, I loved Menardi, and I think the good Proxian would be better off as a female character.
Also pull a Matthew, make these two characters resemble Saturos and Menardi, sure they'd have some differences like clothing and such, but still they need the iconic look.
The new Saturos needs to look the part.
The playable Proxian needs to look just as beautiful as Menardi looked, I mean look at this, this is our new Mars Adept that we'll be playing as.

I'm not Menardi, I just look like her, my name is currently unreleased because I'm not designed yet, but I am currently training how to use a Death Scythe and some cool Mars Psynergy only Proxians can use, plus face it, I'd be be ten times better than that stupid Tyrell, or that nobody Eoleo.
Same goes with the bad guy.

I'm not Saturos, my name is currently unreleased, but I am totally better than Saturos in every way, Felix is a piece of garbage compared to me, my desire is to rule the world and this Alex seems to know just how to do that, hahaha, bow before me, the new Evil King of Weyard, hahaha!