I know for a fact that changing out the daggerboard trunks in an A-cat of ANY age costs a bit more than $1000. The shape of the hole won't change that cost very much. New symmetrical 70 mm boards are about $1000 per pair. Banana boards might cost a bit more than that, but you might have a competitive boat again for 2+K dollars, then adding a good sail. This seems like a fantastic bargain to me, noting that some sailing skill is involved.
The wingsail is pretty to look at, but rather like Paris Hilton, I wouldn't want to own one, class legal or not.