I've got one bike now that was listed as a hybrid, but has CX geometry that fits 38's, and two more that originally wore 27X1-1/4 tires that have such huge reaches that it would literally be impossible to fit 650b on them due to brake reach. Either of those could easily take 40mm 700c tires. But then again, those are pretty low end (UO-8 and Raleigh Rapide mixte).

Got a World TOurist also that could probably take 35-38's...

ETA: Something else to consider...what would the weight be of a pair of 650b wheels and good tires (hetre, CdlV, etc) compared to 700c wheels and comparable tires? I know the 700X38's I was riding on the CX/hybrid nearly killed me after about 10 miles because they were so bloody heavy and resistance crazy. I could triple my distance at a given speed switching from 38's to 28's on the same bike with the same wheels.