Stacked airbags

[jeromio]

I've been searching all over for this and I've come up completely empty. It seems (to me) like an obvious solution to the problem(s) of airbag suspensions: the less air pressure, the lower the ride height AND the lower the spring rate. So, super low, you're either on the bump stops (not good), or you're warbling all over with no control (also not good). And then the reverse: max ride height is also max spring rate (jacked up but way too stiff).

So, I'm wondering why you can't just stack 2 airbags, meaning individual airbags each with their own separate air inlet (one on top and one on the bottom). So with one bag completely aired out, the ride height drops, but the 2nd bag provides a relatively usable spring rate. One spring maxed out for lift would leave the 2nd to provide some compliance.

Why is this not something that you can just order off the shelf? Am I missing some important detail?