I agree with Alec. Don't block the existing tor2web stuff, that would be very rude. Instead just do not implement any kind of tor2web for v3 onion services so that tor2web will gradually fade as we migrate.

*although speaking as a geek I believe that re-engineering T2W to support SSL via SNI-Sniffing would address this, it would be a gross and pointless hack, complicated still further by certificate issuance, and all reasonable use cases for which would be better addressed by running a local copy of Tor.

Ah yeah, Donncha wrote a tool to do that called oniongateway:

https://github.com/DonnchaC/oniongateway

Is that what you mean?