I think it'd be okay, the only thing I'd be nervous about is chemicals! So just make sure they're not using things that have had chemicals and such on them and they're not using glass cleaner on it.
Also, you'd have to attach it inside the tank with something like silicone sealant. So hopefully you have someone for that. Fiberglass can be really sharp, I'd be careful for you're sake! Make sure they can't jump over it, too.
Other than that, I think that's a VERY good idea!
I use seran wraps for tops of tanks usually ones I find on sale due to their lack of top, I'm altering filters personally and make my own parts when I lose one or it breaks, and I use things at home for decorating.