Dock lines become jack lines
We leave two bow and two stern lines on their cleats through the season. When we get under way, we pull each bowline back down the deck. Then we pull a loop of the stern line forward and tie a loop of the bow line around the stern line. Then we pull the stern line loop tight on its cleat and make it fast there.
The result is a jack line that runs from the cockpit to the bow on each side. We also have a hard point on the forward bulkhead of the cockpit. Although round, it hugs the side of the cabin, so no problem under foot. Our rule is that the captain must be tethered, unless there is another helms person who has practiced the MOB drill on Lady Lillie. Despite her qualifications, the Admiral has declared herself unqualified, so I am tethered unless I go below while we are under way. We use inflatable PFD's with built in harnesses, so this is not a big deal. In rough weather (waves over 3 ft.), all crew use a tether to go forward.
I agree that centerline jack lines are the best, but haven't rigged the necessary hard point(s ?) yet. One issue is how to work around the sliding hatch. Always something! The solution for single handing is to secure the aft ladder with a piece of light yarn, so I could pull on the ladder and break the yarn to deploy the ladder from the water.