Steve Lusardi wrote:

Bonding your
throughhull fittings will even make the corrosion rate faster.

Steve, omitting all the boats that are bonded or unbonded & various
circumstances & results, I am wondering if it is std practice to
calculate & size anodic protection in terms of current & exposed metal
areas as in commercial practice? (apart from any other considerations
of galvanic currents from neighboring boats/docks/power grounds/etc.)

The use of metal throughulls adds no additional value.
There are some exceptional high quality plastic ball valves used in the
corrosive chemical industry, which would make the entire problem go away.

Would seem wise & even moreso if ball valves are to be used. The
disadvantages of a bronze through-hull combined with those of a
bronze-bodied SS ball valve seem counterproductive all the way around.