If I understand your goals, removing some of the casting platform to convert to split bench seating with a walk up the center to the bow, it sounds doable. You should be able to remove the hatch and cut away the center of the casting platform. You’ll need to create a floor between the stringers forward. Then you can use glass panels or glass covered foam or honeycomb. Tab in the new pieces and glass. I assume, you’ll wa t to add hatches to access storage under the benches. These could be anything from ready made after market hatches or custom that you build yourself.
If your deck transom and stringers are in good shape, it’s a moderately difficult job. Keep in mind that this is coming from someone with megalomaniacal rebuild tendencies. But it is definitely doable.
Oh, it’s not a thwart on a powerboat, but I believe you’re referring to the bulkhead at the aft end of the casting deck. Adding the section of deck across the stringers will more than compensate for cutting the bulkhead.
