The story and gameplay of ARENA doesn't really hold up that well by modern standards. It may have been "BIG", geography wise, but it would not be worth the effort. That game world, as-is, but with prettier graphics, just would not be very cool. It was FLAT. Completely FLAT. Towns were identical in architecture on the most part.
Better to do the same thing, but skip the "ARENA" part, and just make up a new story and updated interpretation of the landscape. Everything would have to be re-mapped, re-landscaped and re-written anyway. Might as well make it GOOD.