That's not a terrible idea. Not sure how much you could lift as high as you need it, but when I was selling new homes, we had balloons we called "cloud busters" they were probably 3' across, and they'd lift that heavy streamer (think the stuff car lots use with the little triangle flags) a couple hundred feet up. I pulled it down at night, and put it in the model home garage. It would last about 3 weeks and didn't lose too much lift over that time.
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