The split hatch idea is okay, but you still have the hassle of climbing over the engine in the engine room and removing the nuts and washers holding down the aft section in order to remove it.
The "Hatch in the Hatch" idea is nice, except for the expense of the hatch (I suppose you could always get a used one) and the fact that the hole is so much smaller. It's reall roomy for work when you pull the whole cockpit floor out.
I have an idea I am going to look into - putting threaded inserts in the deck (sort of like captive nuts) and using round headed set screws from the top, maybe with rubber washers. The screws have the round head of a carriage bolt with a hex hole in them. Then all 24 could come out easily using an Allen wrench socket in an electric screw gun or a speed handle.