So, I finally got a 3 page long, illustrated pdf (I contemplated attaching it, but I think at this point it would be more 'laughing at instead of laughing with' the person, and I'm not really wanting that) write up of the character concept.
It was very detailed and completely not anything like a D&D character. I mean, possible a pathway to some high-level goal or something, but it really seems like this person had zero understanding of what a D&D character is.
My reply:
That's a lot of concepts for a new character.
I really don't think that is going to work. Do you have access to a 2014 5E Player's Handbook? If not, I can help you with a character build.
D&D can be very extensible and get into whatever things the players and DM want to, however, this is a mostly newby group so we're sticking to a fairly standard set of rules so that no one ends up feeling left out or overshadowed by other player characters.
Even if this character race worked in my game world (it really doesn't, but I can always handwave that with "a portal opened, and out you popped" if needed) it would take a lot, and I mean a lot of work to get that character concept into a format that would work and be balanced. More work than I'm really capable of doing without some serious playtesting. If this were a mature (play experience-wise, not necessarily age) group, then I might wing it and see how it goes, however this isn't that group.
If possible, could you look through the core races and classes and stick to those for this game? Sorry if this isn't the answer you wanted to hear.
I've also decided to send out a group message to say that for this game, we're sticking with PHB, Sword Coast, & Xanathar's for PC builds just to not show that I'm playing favorites, as I had initially allowed a aasimar and (grudgingly) a golaith. What apparently happened was that most of the group just went on some online D&D character builder and enabled "all options" and went wild. Granted, in the dino case, that wasn't even what happened, as they just wrote some stuff up.