Nope. As I said, if you need a transport layer to connect arbitrary peers over the Internet, TLS is exactly what the doctor ordered and it already exists. Already studied, already got libraries that implement it, already got test frameworks, everything is in place. An alternative even if it was technically no worse (which isn't guaranteed) and available today (impossible) doesn't have those things.
> You can do PKI with plainkeys.
Nope. A PKI specifically involves the binding of keys to identity, that's what the certificates are for. You don't have to have X.509 (though I'll argue you might as well) but you need that binding.