There are quite a few flat bar carbon fiber hybrids coming out. No doubt many more in the next couple of years. But, I see your gearing issue.

Perhaps an option would be to go with the RS700 shifters, Ultegra FD, and Tanpan adapter for the RD of your choice.

Tanpan ? wolftoothcomponents.com

It is also possible your MTB gear would be forgiving with a 2x front end. I see several of the MTB front derailleurs are listed 2X

The road chainrings will be slightly larger than the typical MTB chainrings, but the configurations tend to be fairly forgiving.

Do the Shimano MTB front shifters ratchet, somewhat like the Campy shifters do? If so, they may also be very forgiving for different configs, and mixing and matching derailleurs.