Japan got heavily upgraded projectors (it's visible in all the on ride videos from there), and who knows, in 2 years time, technology will be even more advanced, we could get better projectors than Japan, which a few additional effects.
If it was up to me, I'd use the extra space for a Whomping Willow family spinner ride.
But since that's far fetched (for whatever reason), I'd use that extra space as an extension of Hogsmeade, for extra bathrooms, FJ locker rooms, and maybe an additional snack counter.