It's a disappointment is that humans - particularly Megan, Danny, and Molly - and mythological human-like species didn't return in the later incarnations of My Little Pony after G1... It's understandable that it's due to people's - particularly Lauren Faust - own personal tastes, though, but still. And after Lauren Faust left, the writers could’ve added them later on, but they chose not to for her sake... Either way, none of them returning in G4 - and the other incarnation of My Little Pony - was a total letdown... And, of course, it's always preferable that they returned right away in their debuts. Megan, Danny, and Molly would've been perfect protagonists alongside the Mane Six in G4.
Speaking of mythological human-like species, Tirek didn’t resemble a centaur at all. He doesn't have a human face. Seriously, why did they remove the human parts on every mythological human-like species and replace them with non-human parts? Not only is this idea weird, but it’s also silly and pointless.
Danny has proved himself as the most competent character of My Little Pony. He has authority, he is a leader, he is resourceful, he is stalwart, and everything. He always knows what it will take to keep the ponies safe from all kinds of dangers and foes. Furthermore, he and the ponies had a lot in common together since the beginning, and they would’ve had the same in the later incarnations of My Little Pony, as well.
Danny is the one who created the Magic of Friendship since he's the original Brony, a mare magnet — the one who gets all the mares. So, he's the one who's making the Magic of Friendship grow, especially due to the bond between him and the ponies.
So, Danny is undoubtedly the dominent character of My Little Pony, which is why he is meant to be the king - the supreme leader - in each incarnation of the franchise. In G4, he becomes the king - the supreme leader - of the entire world beyond Equestria later on, as well.
Another idea I have in mind for Danny is to make him a music artist/singer, like Countess Coloratura, Sapphire Shores, and Songbird Serenade.
The franchise had many flaws here and there - even the writers of G4 - I would've done better... So, I'm working on my own concepts and everything for My Little Pony, the true version of the franchise - the addition of humans and mythological human-like species with their human parts untouched - especially Danny. What I'm currently working on is concept arts of actual centaurs, and there'll be two other types of them with unicorn horns and pegasus wings.