I'll add a quick caveat ...
I can see a place for bikes that fit two rim sizes to accommodate different tire widths. For instance, a bike that can fit 406 and 451 tires according to whether you want wide or narrow tires. This would keep the total wheel diameter close ... 406 + 2 * 50 = 506 versus 451 + 2 * 28 = 507 ... and the bottom bracket height roughly the same. Off the top of my head, I imagine that one could build frames for 507/520, 559/584, 584/622.