PrivateKey = !peername

Publickey = !peername

And the actual credentials could be in a separate file with a specific name, with one peer per line:

peername:pubkeystring:privkeystring

That would make deployments much easier, as the credentials could be handled separately.

However, the peer address assignment is another good question. One file per peer would be better, I think, but you'd need something like another directory, and, at that point, you might as well write a script to take all your config and concatenate it into one file. That having been said, I don't know why that can't be a part of wg-quick.