Karlin, the zinc based paint is an interesting idea. Since regular zinc anodes are consumed over time, what is the thinking regarding the zinc in the paint? Wouldn't it be used up if it were actually needed?
The isolation stops between the tank and the bolts also sound good, but if salt water is present, wouldn't the current just lead around the stop? If the stop was something like an insulating glass cup, inverted over the bolt and sealed to keep salt water away from the bolts, I could see how that might work - is the idea something like that?
Good luck with your refit, I'd love to hear about the total outcome when it's done (pic's would be really nice).