The short answer is no, it will fly perfectly fine without but you won't have a lot of features that would get by having them. The basic flight controller gives you altitude hold and autoleveling, if thats all you need for the flying you'll be doing then the other boards can be left out. Position hold, return home, carefree and a lot of other features depend on the Navi/Gps combo and those features you won't have.
Ken