My brainstorm is to reimagine and remake it into a raised bed on top of our flat garage roof. It's heavy with the springs in it. Probably quite a bit/lot lighter without. I'd remove the springs, paint with outdoor paint, fill with lightweight potting soil and plant up with scavenged sedum. The roof should be fine. In the winter we shovel tons of snow from the 3-story porch on to it. No other place for the snow to go. The shallow planter would be much more compact and lighter.
The questions in my mind are:
Is this a good idea?
Is this a bad or dumb idea?
Is my plan doomed to failure?
Will the wood warp or rot in short order in spite of being painted?
What material should I use on the bottom for drainage--lava rock, gravel, or something else?
What other plants would survive hot full sun and wind in a shallow planter?
If anyone has words of advice, direction, or validation I would love to hear from you.