Ooo. Oh no. I mean, it would add some cool variety, but, blimey that'd be hard to keep up with.
Here's something that happens to me a lot. I'm flying a Spire in the Canyons, and we're waiting in out spawn, and suddenly we get rushed, and I go down first. I spawn in again, while they're still in our spawn, and get slaughtered before we can even turn to face them. If I could just switch, midgame, to a Metamidion for some close up killing potential, or a Galleon for something with a little more tank power, that'd be easy for me, but not really fair for the enemy.
Personal loadout/class changing between respawns sounds like a fantastic idea, though. You already can change that stuff midgame, but you have to leave the match first, which is a pain. If you were able to do it more easily, that'd be amazing