If he wants to coast the downward slopes, he doesn’t need to have freewheel on the high speed.
Personally, I think the schlumpf hub with the freewheel in 1:1 gear looks reaaaaaaaally fun, but I think I’ll get one without freewheel… unless I get a 2nd one with a 1:1 freewheel… 
I’ve been thinking about the interest of such a hub for a while, a French engineer has started a project of a 2 speed hub with a 1:1 freewheel and a 2:1 fixed gear (with bevel gears) and hand shifting.