I believe that it would be possible, but I would tread lightly when applying that first layer of fiberglass. If it were to oversaturate your cardstock and tape it could begin to fall apart. I'm sure though that with some patience that you could carefully brush on a little fiberglass at a time. Maybe a test of the process is in order before you proceed?
Also I would reccomend to all the Pepakura/cardstock armor makers that they reinforce their armor with fiberglass cloth from the underside, rather than the exterior. Just brush a light coat of resin on the exterior after it's been reinforced. I think your results will be much cleaner, and preserve tha accuracy of your original paper models.