That is a good idea. You could always get a clownfish, too, as they are damsels and are very hardy. Perculas seem relatively easy to come by and as long as you got a small one, it would be okay in that tank for awhile.
Starfish can come into contact with air and it wont hurt them. Mine climbs to the top all the time. At low tide they are usually exposed on rocks, too. I love stars–that was half the reason I set up a marine tank.