You can sit and play the guitar, it will be a bit uncomfortable at first but youll get acustomed to it. You will have to use a strap while playing, but you should always use one to prevent any accidents...
If you look at the flying v model, youll see underneath the side of the guitar, where it would be resting if you were playing it sitting down, a type of "sanding paper"?? that prevents slipping due to the guitars shape...
nonetheless that guitar was made to be played standing up, and on a personal note, I think that is one of the coolest visual models I have seen on electric guitars...