Hey! A bit late on this one but I wanted to respond for anyone else who still has this question.

I think one of the biggest restrictions when writing "in the round" is the set. Walls, trees, and other large pieces are likely going to be major viewing obstructions. Also, stay away from complicated sets. There are no immediate wings to hide set pieces in for quick changes. I've seen some theaters in the round that actually lower their set pieces from the ceiling via a pulley-type system. Either way, this is not the space where you can write a piece that covers five different locales. That's not to say that you can't still let the setting get creative, but just be careful.