Looking at your original list of requirements, from my experience with years of both kayaking and sail-and-oar boating, three points occur to me:
1....
Don't have a lot of experience with those. How well do they work in northern latitudes, the north Pacific, say, where you can go weeks without seeing...
The "QuenchSea Reel" unit, to which the original link points, is not a pump, per se. It has no moving parts that I can see and requires no pumping by...