Putting the Bathtub Inside the Shower

We've all seen tub/shower combos, but this takes that term to a whole new meaning. Have you ever thought of putting your bathtub inside the shower enclosure? The Japanese have been doing it for years in their wetrooms. The house plan we are building has a set up with the ability to put a bathtub inside the shower door. For the past month, I can't help but wonder if this is pure brilliance or a design mistake. There are a zillion pros and cons sloshing in my head and here's what I've decided so far. What's your opinion? Would you do it?

Pros:

while bathing, there would be a smaller space to heat up in order to stay steamy warm
you can rinse off after a bath easily
even if the space is tight, the shower appears larger than it is
it creates a contemporary and open feel

Cons:

while showering, there would be more space to heat up in order to stay steamy warm
it would be a bigger shower area to clean (especially if you have hard water)
which means more glass to buy (and clean) for the shower
the entire space needs to be tiled or waterproofed, which would cost more money initially

Oh how I love the spa-like look of a glass shower paired with a freestanding bathtub!