This is an idea I came up for a hack of this game, that includes most Pokémon that aren't in any Pokémon Mystery Dungeon series yet.
Here I have a list of Pokémon that will be new to the series and the Pokémon that will be replaced.
All of the Pokémon being replaced are in Gates to Infinity. (Bar Purple Kecleon).
Purrloin (Leafeon)
Liepard (Glaceon)
Pidove (Vaporeon)
Tranquil (Jolteon)
Unfezant (Flareon)
Throh (Ho-Oh)
Sawk (Purugly)
Basculin (Eevee (My be difficult due to being a Starter))
Darumaka (Pikachu (My be difficult due to being a Starter))
Darmanitan (Raichu)
Maractus (Glameow)
Sigilyph (Starmie)
Solosis (Swinub)
Duosion (Piloswine)
Reuniclus (Mamoswine)
Vanillite
Vanillish
Vanilluxe
Deerling (Espeon)
Sawsbuck (Umbreon)
Karrablast (Bagon (May be difficult because it's a plot orientated Pokémon))
Escavalier (Shelgon)
Frillish (Wooper)
Jellicent (Quagsire)
Alomomola (Azumarill (Could be a bit difficult because she's referenced))
Ferroseed (Cranidos)
Ferrothorn (Rampardos)
Tynamo (Wingull)
Eelektrik (Pelliper)
Eelektross (Toxicroak)
Elgyem (Kecleon (Could be difficult because of being a shop keeper and plot orientated))
Beheeyem (Purple Kecleon (Could be difficult because of being a shop keeper and plot orientated))
Shelmet (Croagunk (May be difficult because he's a main Character))
Accelgor (Salamence)
Stunfisk (Pichu)
Bouffalant (Dunsparce)
Heatmor (Marill (May be difficult because he's a plot orientated Pokémon))
Durant (Azurill (May be difficult because he's a plot orientated Pokémon))
Genesect (Lugia)
Unfortunately, not all Unova Pokémon can be added to the series, but I'm willing to switch a few things around.
Note that even though Eevee is being replaced by Basculin, that does not mean Basculin will be a new starter Pokémon, and I'll probably replace Eevee with another brach evo Pokémon.