Improvising a temporary skylight?
I think your Plexiglas would work but I would use Lexan polycarbonate sheet. Lexan is a few more bucks but will not crack when you drill it or something hits it, tree limb baseball ect.
You can heat polycarbonate with a heat gun and bend it. I would do this on the top edge at a minimum. Other than the material I believe your plan will work both short and long term.