I think this is a great direction for the VGC. With Champions having HOME support, the mainline games can continue to add new mechanics without having to worry about balancing for past stuff, while Champions can have all the mechanics in one spot. Train your Pokémon in the mainline games, then send them to Champions for competitions. And with Champions being on mobile devices as well, it expands the player base for VGC very well.
Not to mention, we already know Mega Evolution and Terastalization will be in Champions, but the Omni Ring (the thing used to active those two mechanics in Champions) artwork shows that Z-Moves and (most likely) Dynamax will be in the game too. Having all of those mechanics present can create some very interesting competitions.