Good afternoon. ^^;Â
So I have given a lot of thought to your conundrum here regarding character creation, backstory and general RP questions in the terms of Main Story Quests, the Echo and our positions as Warrior of Light. I'll be honest and start off by saying I've only skimmed the responses that other people have given.Â
Let me first start by saying I don't think you need to change anything about your character or what you'd like for their background. It's very possible to include the majority of what you want for them: such as the adoption, the "unique" naming conventions, the two separate Clan avatars, etc. That being said, I'll address your concerns regarding the Main Story Quest, the Scions, the Echo and the Warrior of Light further down.Â
Let us begin with your background.Â
We have learned that there is at least one tribe of Xaela whom settled in Eorzea. They came, they saw and they made some homes here -- although we do not see them often. We also know of a tribe, from the original Xaela Clan list, whom built ships and traveled across the Eastern ocean; while we cannot be certain what is meant by the "Eastern Ocean", it's unlikely someone will dispute them ending up on Eorzean soils. While the lore itself (which we were given) states that they returned with tales, that does not mean there were some who "got lost" or "left behind".Â
     Now, with that in mind you've a very real possibility of simply making your character Xaela in it's lineage, but born with pale scales. Genetically speaking, this is likely a very rare occurrence and is very likely to be seen a bad omen or "curse" by members of the tribe, depending. This however, does lead into the realm of being adopted by Eorzean parents and given "new names".Â
As for other tribes whom interacted with Raen, there are a couple options.
You do have the option of the Kha tribe, whom often incorporate Raen/Doman cultures into there own. It would not be unheard of for a member of this tribe to "fall in love" with a woman born of Raen/Doman descent (or vice versa) and produce children. This would be very similar to the Malaguld tribe -- with the Raen/Doman outcast having been brought into the tribe; however, these two tribes have a slimmer chance (slimmer, not impossible) of winding up on Eorzean soils during a key point in time in your characters history.Â
     That being said, there is no reason that something "tragic" could have happened to send the boys away from their tribes or the boys could have more recently become familiar with Eorzeans and their cultures, taking a shine to them as it were and leading to a more recent "adoption" with people who may have made them feel more at home. There is nothing that says a person born to a Xaela tribe or a Raen Clan has to feel "at home" with their people; everyone is different at the end of the day.Â
Now, all of that being said, we'll move on to the main chunk of your inquiries. ^^;Â
I'll start with the first point you bring in: drawing and the possibility of Alphinaud playing some role. This will go hand-in-hand with the question regarding the Scions and your inquiry regarding the Main Story Quest.Â
      What I have learned over the years of RPing is this "golden rule": You are not the Warrior of Light and the Main Story Quest is a mechanic. What this means is generally speaking people whom Role-Play on MMO's do not "openly" RP what they experience in the game when it comes to Main Stories or "being the main hero". There is always the exception of people who get together groups to support such, but the vast majority of people have a tendency to turn their nose up at someone walking around in-game as the Warrior of Light. I have seen this first-hand, where someone was RPing that they'd accomplished everything they did in the Main Story Quest and the people they interacted with were vastly opposed and it led to some ridicule. I am not saying this is the fate for people who go that route, but it does seem the majority of people go with the generic mercenary/adventurer route. As I use to put in World of Warcraft: we are the nameless, faceless adventurer who are never given credit.Â
      What this means is that, while you could have done great deeds, it's unlikely anybody would recognize you outside of a few key items -- which I will get into now. Grand Company Standings are a thing and many people RP their appropriate ranks to a degree. I have encountered a large number of people who role-play their connections to the Immortal Flames, the Maelstrom and the Twin Adders. Generally, the people I have encountered role-play positions such as officer or lieutenant; they are recognized as "official" members, but do walk a very thin line with some of the community as playing a person of power can sometimes go to one's head and cause quite the back-lash from people who feel the lore is being "abused".Â
In my opinion, there is nothing wrong with role-playing your accomplishments in game. If you spend hours at the Hunt Board, there is nothing wrong (in my opinion) with role-playing that you've accomplished some of these hunts. While they won't garner you a lot of attention, it is possible that NPC's would recognize you as one of the Hunters who frequents those boards. It also has the potential to lead to very interest and very immersive role-play.Â
Now, with that out of the way. The Scions are similar to celebrities in modern day with a few changes. It's very possible that your character could have seen them in passing -- as there are a number of times during the Main Story Quest that you speak with them in populated areas. This being said, it's very possible to role-play having seen not only the Scions, but having seen the Warrior of Light as well.Â
     Your character's love of art could have led them to sketch out having seen Alphinaud as they might idolize them. So while you've never actually interacted with them, they are still a part of your history and a detail that can easily be used to strike up role-play: "I saw them once, the Scions. Thancred is shorter than I would've expected."
I know not everyone will always agree with the choices you make, but it is very possible to remain within the realm of lore and still produce a character who fits everything you want.Â
Lets talk about The Echo and all the fun there.Â
The Echo doesn't always manifest in the same way. There are different forms/types of the Echo. We see this within the Main Story Quest, when Minfilia basically tells you that as the Warrior of Light, the manifestation of your Echo is the "rarest" of all forms -- and that is essentially what makes you the Warrior of Light.Â
     I have seen several people who've allowed themselves to possess the Echo in-character, in various ways. The majority of them often go with a "weaker" manifestation than those seen in the Main Story Quests and with the Scions themselves. The chances of having a very rare manifestation of the Echo alongside everything else you've designed for your character is infinitely small, if I am to be direct. Balance is key when creating and engaging people in role-play. Too many unique qualities and the balance becomes unstable.Â
Alright, with all of that being said... we come to the final note you've inquired about: the Dark Knight Soul-stone. As I understand it (and mind you, I had to ask a few friends who've done the story-quest as I have not) through the Dark Knight quest-line you acquired your soul-stone from a deceased Dark Knight.Â
      In the realm of possibilities (alongside the realm of in-game lore), Dark Knights are not a common feature of Ishgard (labeled as Heretics to the Holy See and sentenced to execution upon sight -- or so I've been told) and their rarity seems to be quite high. That being said, regardless of rarity I cannot truly debate the possibility of finding the soul-stone of a deceased Dark Knight in the world: likely near one of the more fabled marks (from a mechanic standpoint: World Bosses). Sometimes, even the most experienced man (or woman) can become a little too big for their britches.Â
      As for not knowing what the soul-stone is precisely, this is a thin line. Hallucinations are the biggest "problem" of them and could potentially lead to your character believing this stone to be cursed -- now whether that draws them to it or sends them fleeing is entirely your choice. If it draws your character in, there's nothing that says going home could be a means of trying not to lose themselves to the hallucinations while also hoping the homeland might provide information about the stone?
There are many routes to travel when it comes to squeezing something unique into the game's lore and I've come to learn that there are a lot of very tolerable people in the role-play community (at least on Balmung where I am stationed), especially when it comes to something being well written and well thought out. Research is the number one thing you can do when wanting to squeeze in unique facts/details about your character.Â
      I will offer you this last warning, because it hits very close to home for me personally. There is very little Hingashi lore available.Â