There are days when no one wants to play the big stupid fighter. Why let that stop you from having fun? Play right and you don't need them anyways. Many classes can be replaced with judicious usage of other class abilities. Like the druid's animal companion. Good replacement for many of the martial classes. With an all wizard party you have to be much more careful though. Nobody can soak a hit and until you hit higher levels summoning a spare meatshield isn't entirely feasible. But once it is, then you can completely go to town.