I hope Kingdra can keep Sharpedo in check though, else i worry about Gohs other Water Pokemon that swim in the lake (If Kingdra can't, Poliwag better evolves into Poliwrath fast) and i hope Kingdra never meets Dragonite.
I don't think it works that way though. I mean, the Pokemon being turned into eggs are most likely Grookey, Eevee and Piplup and maybe Dracovish or Buneary (Unless Goh takes Mantyke with him), because Pikachu only becomes a Pichu, which means the 3 stages would only go back one stage.
Kanto - Kingler (It needs its redemption and hasn't been used in any major battle since the Kanto League)
Johto - This is a hard one, since the only one eligible imo are Totodile, Bayleef and Quilava (Due to LA promotion). But i personally would prefer Bayleef.
Hoenn - Glalie (For obvious...