Maybe a vector of vectors would be a better representation here:
(define new-board
(list->vector
(map list->vector
'((P2 OFF P2 OFF P2 OFF P2 OFF)
(OFF P2 OFF P2 OFF P2 OFF P2)
(P2 OFF P2 OFF P2 OFF P2 OFF)
(OFF BLANK OFF BLANK OFF BLANK OFF BLANK)
(BLANK OFF BLANK OFF BLANK OFF BLANK OFF)
(OFF P1 OFF P1 OFF P1 OFF P1)
(P1 OFF P1 OFF P1 OFF P1 OFF)
(OFF P1 OFF P1 OFF P1 OFF P1)))))
(define (get-state board x y)
(vector-ref (vector-ref board x) y))
(define (set-state! board x y val)
(vector-set! (vector-ref board x) y val))
then
> (get-state new-board 0 1)
OFF
> (get-state new-board 1 1)
P2
> (set-state! new-board 1 1 'hi)
> (get-state new-board 1 1)
'hi