This "faithful remake" term made me realize one thing:
No Pokémon remake takes advantage of the expanded roster.
In FRLG: Gen 2 and 3 Pokémon are only avaliable in the post-game, you need the National Pokédex to get them, to the extreme that the game will physically prevent you from getting them if you don't have the NatDex (you can't even trade with RS without having the right key items)
In HGSS: Gen 3 and 4 Pokémon can be obtained, but only in the post-game, via the "Hoenn Sound" and "Sinnoh Sound" thing, and the options are limited. Outside of that, everyone has the same roster as before. Morty still uses two Gastly, one Haunter and one Gengar when he could very well use Gastly, Misdravus, Duskull and Drifloon
In ORAS: Gens 4-6 are Pokémon are in the game, but require transferring/trading to obtain...
Rather than remaking the roster from scratch, they treat the new Pokémon as nothing more than bonuses, not helped by the "you can just transfer" mindset encouraging this practice. And if it's to treat the Pokémon this way, don't bother programming then into the game at all. That's what other Mon games do, and it works for them, why it wouldn't work for Pokémon?