Well, the idea isn't that you're carrying an entire squad, no. You're still only having three pokémon with you at all times -- you'd just be able to switch them out for three others, but only when you go back to the main building. So you're not switching them out on the fly -- but you still get to have some variety, which is nice if you're planning on being in the zone for awhile -- like in Blade's or MLG's cases.
[Edit] Oshi, 7000 posts get!