I think that there is a market for almost anything that you can attach to a boat.
Back when I worked, I wanted to do a number of projects. However, I made more money going to work (commission sales) than I could have made by staying home a day and doing some boat add-on.
So, if you can produce it and SHIP it (big issue these days) for a reasonable price, someone will buy it.
As was mentioned above, though, lots of the guys/gals on this site are inveterate do-it-yourselfers. richg99
p.s. I noticed a few posts above, someone has an extra aluminum seat, that would fit almost any boat. There were a number of quick interested parties for that object.
I wonder if you could produce a similar sized seat, with or without the cushions, for a price that would bring the buyers out? AND, can you advertise it here or elsewhere so people can find out about it? AS you know, everything costs $$$$
Might be a trial project.