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 or
www.arccompany.co.uk) 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.