
Though the existence of hybrids is plausible (given evidence you already mentioned), it's also very very rare, if we consider the NPCs we have access to in the game to be any indication of population density. Thus, while playing a hybrid isn't in any way lorebreaking, you will doom yourself to the following two probable situations coming up on a regular basis:
1. Some players will consider it snowflakey, especially if the fact of being a hybrid seems irrelevant to the character's story/background. If it's a major component and arguably defines their outlook on the world and the manner in which they interact with others and pursue goals, then it will seem less snowflakey because it becomes a critical plot point rather than a cosmetic detail.
2. You will have to constantly, and repetitively, make note of whatever prominent visible features exist on the character which other characters can see, but you can't represent on the avatar. For example, when playing a hybrid hyur/elezen, if you use a hyur avatar, you'll have to constantly include in your emotes references to the character's pointed ears, lanky limbs, etc. On the other hand, if you use an elezen avatar, you'll have to constantly reference the character's rounded ears and squatter-than-elezen limbs. This is the only way to ensure that other players can recognize you're playing a hybrid (putting it in your search info or wiki isn't enough - many won't look and will just assume the character is the race represented by the avatar).
If those two things are palatable to you to endure on a routine basis, then you'll be just fine.
1. Some players will consider it snowflakey, especially if the fact of being a hybrid seems irrelevant to the character's story/background. If it's a major component and arguably defines their outlook on the world and the manner in which they interact with others and pursue goals, then it will seem less snowflakey because it becomes a critical plot point rather than a cosmetic detail.
2. You will have to constantly, and repetitively, make note of whatever prominent visible features exist on the character which other characters can see, but you can't represent on the avatar. For example, when playing a hybrid hyur/elezen, if you use a hyur avatar, you'll have to constantly include in your emotes references to the character's pointed ears, lanky limbs, etc. On the other hand, if you use an elezen avatar, you'll have to constantly reference the character's rounded ears and squatter-than-elezen limbs. This is the only way to ensure that other players can recognize you're playing a hybrid (putting it in your search info or wiki isn't enough - many won't look and will just assume the character is the race represented by the avatar).
If those two things are palatable to you to endure on a routine basis, then you'll be just fine.

Lydia Lightfoot ~ The Reliquarian's Guild «Relic» ~ Lavender Beds, Ward 12, #41
This player has a sense of humor. If the content of the post suggests otherwise, please err on the side of amusement and friendship, because that's almost certainly the intent. We're all on the same team: Team Roleplayer! Have a smile, have a chuckle, and have a slice of pie. Isn't pie great?
This player has a sense of humor. If the content of the post suggests otherwise, please err on the side of amusement and friendship, because that's almost certainly the intent. We're all on the same team: Team Roleplayer! Have a smile, have a chuckle, and have a slice of pie. Isn't pie great?