This is kinda hard to explain so maybe this will help

Between now and when I re-assemble the tank I'm going to construct a small "island" roughly 1' x 2' to go on one side of the tank. There willk be 3 pieces of PVC holding it up. the top will probably be a 5g lid cover cut to size. I'm going to use different sized PVC pipe's and aquarium safe glue to coat them in sand to them so the fiddlers have something to grab on to, and it looks a bit more natural. I also plan to cut holes through the thick main support so the fish can use it as a cave.
Lower the water level about 1/3rd of the tank, put the island just below sea level, use aquarium safe glue and glue sand to it as well so it looks more natural, and then put sand on it. There will be two "access" points for the crabs to get onto the island and I'm debating about using a spare water pump to make a waterfall. That's about it so far. Those are the plans.
Ohh and I'm gonna take a few PVC T-joints, like 6" round, cut em length wise, coat em in sand and put them on the ground so they will act as caves for my dragon goby because I'm getting rid of the crappy fake rock structure he currently lives under.