I did speak to Kinesis about if that was an option:-
Being our flagship, endurance, road bike, we haven’t tested a GTD frame with 650b wheels as far as I know. It was designed around 700c wheels.
Due to the frame and fork design with slim, curved stays and fork blades, I don’t think you would get a huge increase in tyre size if 650 wheels were fitted and this would leave the bike sitting very low which wouldn’t be great for the geo.
I would recommend sticking with 700c wheels and the current GTD V2 will take up to 34mm tyres which opens up some tyre options that will be capable of light gravel riding. Something like the Challenge Gravel Grinder in 33mm would be a fine choice for fast, summer Gravel rides and wouldn’t slow you down much on the road either.