Heh, I actually wanted to built this when the article first came out, but the problem was that this requires higher water temperatures, which my solar-thermal water heater only reaches very rarely and are impossible to reach with normal hot water heat-pumps.
As long as the billionaire class can live without repercussions I'm very hesitant to judge someone on taking a bath instead of a shower.
We use paper straws and shower instead of taking a bath and they enjoy private jets, pools and jacuzzis.
Taking a bath is not only hygiene, imho it's also a break from our everyday grind.
Considering my electric shower is hell bent on boiling me unless I turn it to "cold", I feel reasonably confident I could build one of these! Oh boy new project! Time to convince my partner that it's not crazy...