That’s sounding like building a better Mouse Trap. But mine only cost $1.00 plus beer.
My concern would be the purpose for the scupper is to drain water out of the boat fast. This multi purpose through hull fitting is going to trap water inside the boat. In a emergency you need water to go out fast and you might not be available to turn things around quickly with your multi purpose fitting. I will not plug my scuppers up with a plug for this very reason I just wanted the water to go out not in.
I would go the traditional way with a scoop on the bottom of the hull with shut off valve and then live well pump and wash down pump attached to it.
FellowShip
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My motto: Just for the Grins