You are thinking very wrong about what they would do with a remake. It is possible that it would have an entirely different pool of usable Pokemon(as in having ones not in Sword and Shield buy missing ones in Sword and Shield), and they could do the same with moves as well. The other Switch Titles, Let's Go Pikachu and Eevee, have both Pokemon and moves in it that are not in Sword and Shield, why couldn't they, for example, only have the first 493 Pokemon and have all moves that existed in Gen IV available(similar to how Let's Go had all of the Gen I moves available), on top of newer moves from after those games. Many of the missing moves in Sword and Shield are still partially or fully coded to work, they just have no programmed animations and an arbitrary lockout flag preventing their use without romhacking. Missing Abilities are also fully functional, and there is still data for the missing Pokemon, they just have no models and their Gen VII level up moveset(including moves missing in Sword and Shield)