I had a long chat with Arthur Keeling a few decades ago, he explained how he rebuilt a Lambda wheel with araldite, just building it up, layer by layer and sanding back as necessary. If I recall correctly the finish was black cellulose spray. Needless to say, it, being done by Arthur, was a faultless job!! I do not know which would be easier, I think James, your fibre glass resin, with a little fine filler as necessary would be the best option. As a matter of interest James, what type of paint was used for the finish?
Andy