I guess it depends on the definition of "main battery." In some places I see that specified as the guns in the turrets or the armament that the vessel was designed around. In others it's the largest caliber weapons. The wording of rule #9 includes casemates so, that seems to rule out the definition only being turreted guns. 9D is annoying though because I can see why one could say the aft casemates on an EQ are near the waterline.
The casemates are lower to the water so, having cannons in them would give one a better chance of hitting one's opponent near or below the waterline. The aft turret is at least an inch higher and doesn't afford a good down angle. In hindsight, it's not a good beginner ship and the one I bought had issues with the fiberglass resin not having cured properly. Se la vie!
I would think having a ship with suboptimal gun placement would be better than not being able to battle the ship at all. At the end of the day, having one ship on the water is four times as much fun as two on the bench. But then again, I like to battle so I might be a bit biased.
Nope. Not worth the effort. I'm tempted to smash the thing every time I walk past it! The only reason I've kept it is to measure the lines and maybe make a 1/96th scale version, someday.