I am not familiar with Mercer and SOHO, but it sounds like a cool move.
I love your analogy of "Omotesando-cool vs Ginza traditional". ha ha! Exactly, no watch store in Ginza (or in all of Japan AFAIK) has a "living room" feel.
JP Journe Omotesando is also ocreated of the same DNA as this Mercer Street boutique (2 floors, wood, funky, sofa, and chocolate!).
At the Omotesando boutique, I was lucky enough to make an appointment, see the boutique, discuss options, place an order while seated in the comfy sofa, and then finally get my Octo Luna about 1 year later, thanks to the outstanding manager.
Journe, I assume at all its boutiques worlwide, raises the entire visiting/purchasing experience to a level that can't be experienced elsewhere.
Very classy operation IMO.