Decided to think over this chart I made before and try to come up with better replacements for DR characters.
I replaced all schoolchildren except for the CMC, since they alone kinda fit into the story. Now, let me go over the exact changes I made.

Hajime Hinata — Stygian
Honestly, why didn't I think of that before? He fits perfectly! His "pony of shadow" form is essentially Izuru Kamukura.

Chiaki Nanami — Gabby
Cute, helpful, a bit cloud-headed.

Sonia Nevermind — Silverstream
No changes here, it's a good fit.

Akane Owari — Yona
Same as well.

Hiyoko Saionji — Scootaloo
Now, Hiyoko, Ibuki and Mahiru all have a history together, that's why the CMC will work best with this trio. Scoots is Hiyoko, since she was shown to be a capable dancer.

Gundham Tanaka — Gallus
As before.

Kazuichi Soda — Star Tracker
Geek, probably a technophile too.

Mahiru Koizumi — Apple Bloom
Another part of the trio.

Teruteru Hanamura — Pistachio
Country boy with big dreams of a big city and a big career! Thanks for this new character, "Best Gift Ever"!

Nagito Komaeda — Sandbar
Nothing to change here, the best fit of them all!

Nekomaru Nidai — Iron Will
I did not want to include any, uh, old characters, but I'll let this one. They have too much in common: loud, trainers, huge and bulky.

Ibuki Mioda — Sweetie Belle
Remains even with the changes mentioned before.

Peko Pekoyama — Smolder
Since Fuyuhiko is now Spike (more on that below), Smolder fits here quite well.

Mikan Tsumiki — Marble Pie
Shy and possibly a yandere.

Fuyuhiko Kuzuryu — Spike
Smlolder's young master and a heir to the Dragon throne! Probably. Wants to be tough but looks cute as a baby.

The Ultimate Impostor — Ocellus
Stays the same, but without Tiara as an exterior.