I should be more clear. I agree that 3 vs 3 *trainer* battles are a clustered mess but I meant a 2 vs 7 wild pokemon battle. Your starter and Golem vs 5 Golbats or something. Trainer battles should stay 1 vs 1 (2 at most).
1 v 1 Fine 2 v 2 Nice Twist 3 v 3 Pushing it, almost too chaotic. Rotation ? 4 v 4 No
Imagine vsing a team of Aerodactyl Gliscor Landorous Lunatone (?) All of them use Earthquake. Any of your non-flying/Levitate Pokémon would be decimated and you're down to 2 Pokémon left at worst. Just no.
The only further I could see it going is if they had mob-style battle where they had 6 v 6, but it was gameplay almost like Mystery Dungeon and position changing would occur and only one/two Pokémon could a ttack a turn.