Yea, unless you are below 5 foot there wouldn't be enough head room. I already have a hard enough time with soda bottles and I am only 5'10". Do not think they would do much good as the bags would have to be at least 3-4 inches tall to be of any sort of useful purpose.
and yes I have ridden in a civilian semi with airbag seats and have driven a HEMMT with spring loaded seats across 700 miles of Kuwait/Iraqi back roads back in 2003. They are cool, but again don' think there would be any way to have functional air bag seats in a small car of any kind.
sig pic courtesy of GBALT05