Re: Spray on glass???
You can do it, and I'd be surprised if some manufacturer hadn't done it in production, just making a line of sprayed glass fibers where a stringer should go.
It would be "strong enough" if you increased the layup thickness of the stringers until you had the strength needed. Heavy.
If you're just talking about spraying stringers in place to cover them, lots of manufacturers do that. It doesn't give a lot of strength nor give very good waterproofing, IE it's not a great idea.
Erik