You are making a big point of Structural Fillets. If I were doing this layup I would mix a thick batch of high density and do a larger than normal fillet in the corners. Then run the reinforcing fabric on top of the fillet. Is that what you going on about?
There is a big issue that hasn't been mentioned.
You've got five options. Don't do it, Do it wrong. Almost do it right, Do it right, Over do it in terms of installation.
The last two might save the day. The first three may sink the boat. Unless you get your attachment point right on the shear...
So the obvious difference between this and your design is the number of fasteners & the fasteners spread the load a far distance towards the bow. They are also up right on the deck where the load is driven directly into the corner & around.
If you go to a decent structural engineer and...
Your original description of construction would be suitable for a load pulling nearly square from the transom. Basically adding some thickened filler to get a flat/smooth surface then bonding on a serious backing plate.
As others have noted that is not what you need to engineer.