From this:
(https://live.staticflickr.com/65535/52862702000_1b149a675a_c.jpg) (https://flic.kr/p/2oxiaAy)Nomad 700c (https://flic.kr/p/2oxiaAy) by Paul (https://www.flickr.com/photos/phbike/), on Flickr
To this:
(https://live.staticflickr.com/65535/52861734382_cb73fd137e_c.jpg) (https://flic.kr/p/2oxdcXu)Nomad 650B (https://flic.kr/p/2oxdcXu) by Paul (https://www.flickr.com/photos/phbike/), on Flickr
Why? Good question, I'm not sure - to differentiate from the Mercury, curiosity, increased clearance... I considered it from the time I bought the frame last July, but the argument against was that the hubs were already built into 700c, time will tell if that becomes an issue...
Was it a good idea? I'm undecided! it is noticeably more comfortable off road, though just as noticeably slower on road. Tyres have remained Almotions, 700 x 40 to 650 x 55. Much more clearance under the guards, though I still managed to clog it up on one muddy trail, though that would probably have happened to any bike with guards.
If I rebuild a 700c disc front wheel, I could run the Nomad in either configuration, the Mercury wheel would be a straight swap between them. I might do that for fun, I only need a hub, or I might wait till I have a use for that, like if I want to do a mostly on road camping tour... or something...