These are couple of bikes that I’ve built from scratch as all-year/all-weather/all-sh*t UK roads training/commuting bikes.
One bike is based on a On-One Inbred and the other one on a retro Corratec Tange Cr-Mo frame.
Typically an MTB frame needs to be one or two sizes smaller for the right reach (hoods/drops).
They both ride brilliantly and float over everything and the level of comfort, grip and confidence is in a completely different league. IMO they make far more sense than most of “proper” road bikes especially with my shaven Racing Ralphs that allow me to clock 18.5-20.0 mph on my commute. They also make excellent gravel bikes.
For anyone interested, there are plenty of retro frames/bikes on Ebay that would make great candidates, e.g. Marin, Kona…
700C is really not the only way to go 🙂