> This reduces the MITM to the initial handshake.
Mostly. No matter much you trim your certificate chain, there's nothing preventing Google/your bank/Amazon/etc from sharing their private key with, say, Uncle Sam. However, the backdoor admin access that the gov't gets to sites like TwitterFace and Gmail probably makes that a pointless effort.
Confidentiality/Authenticity are pretty much impossible to guarantee unless you control everything on both ends.