Hi Chris-
: 1) Keep the oak, try to sand and plane it to make it fit, and hope it will be
: strong enough by the time I add glass and epoxy

I wouldn't pursue that option unless you can fill all the voids in the oak plywood. It just won't be strong enough.

: 2) Buy another sheet of maple and do the whole deck in maple.

OK, as long as the maple does not have voids. Shine a bright light behind the panels to see if there are any voids.

: 3) Forget the plywood deck entirely and strip the deck.

Sure would look pretty and a perfectly cool way to go. May do that with my Cirrus, definitely doing that with my Merganser 16' project.

: 4) Try to use the maple ply for the two inner sections and strips to replace
: the outer sections.

Haven't seen that done before. Would probably work and would present an interesting aesthetic challenge. Chance for some creative deck work.

Jim