As someone with a low-to-the ground coop such as myself can tell you, bending over to collect eggs and clean out the coop gets really old really fast. I got my first coop a year ago and have already replaced it with a much taller one. You'd think I'm an old fart by this post, but I'm only 40 and healthy! Food for thought.
Personally, I am a fan of the playhouse coops though. They don't attract the wrong kind of attention and depending on climate, can make a lot of sense. There is a thread somewhere on here with a lot of playhouse coops. I would just get something bigger off Craigslist and go from there. I have my chicken tractor on a slab of wood with sand to keep critters out. That would work for a bottomless playhouse.
Good luck!