Sometimes the most difficult way is the best way. If your windlass power cables need extending, I would pull new cables by attaching the new cable to the current one with famous ducttape and pull back carefully the old cable, feeding the new one, and thus install a new one entirely to the connectors near the switchboard. In that way you avoid corrosion and bad connection in the high current power supply and do you make sure your boat does not start to become a DIY ship… but that’s my thought..