Build them with a door small enough that the really fat members cant squeeze their big azz in there. I will never forget that lesson my Dad taught me when I was younger and he had a member that had this big fat girlfriend that he didn't really care for and he always built the doors small enough that she could not fit her butt through there.

But seriously, put you some plexi glass 1/4" thick with hinges so you can open and close from the inside. Also, a platform is really convenient with a ladder made of 4x4s or steps. I have a modular design I use where you build all the panels and then just screw them together on site, including the roof. If you can get access to an old rubbermaid storage building, cut the siding to size and it will never rot. I also prefer the platform to be at least 8' off the ground but I prefer 10'.

Here is one I built a couple of years ago and it has held up fine.