As others have mentioned, it looks more like a conventional blue anti-foul paint than it does Coppercoat. Our Coppercoat product does go blue at the waterline, but lower down it stays a dark green colour.
This being the case I'd suggest removing it, as it's anti-foul properties are spent (and you don't need them anyway given the your pattern of use). You should also see a slight performance gain by removing this layer of rough, absorbant paint.
This can be achieved by hand using a scrapper and a sander, but blasting (soda or dry-ice) is quicker. As long as you use an experienced marine blaster (for example, www.symblast.com
) they'll be no damage to the gelcoat. We have several hundred GRP boats blast cleaned in the UK each year without damage, but employing a skilled operator is key.