Let's see ...small footprint an I can place ESC nearly anywhere and the cap (required by all for proper function) externally, where and how I like, or a brick with the cap inside that does not fit without stacking electronics.
If that little cap bothers you so much then I think I hear Nitro calling you, you know with the starter boxes, glowplugs, fuel filters and those damn pesky carbs sticking out of the those engines.