Re: Multi-headed bowls? Mixing? What?!
For the most part, it's a waste: it takes x4 the shisha and coals, plus that means you must do the heat management on 4 bowls. Forget about windcovers, so you'll really have to johnny-on-the-spot with moving the coals or it's burnt city.
For the most part, almost everyone will say the same thing - it's nor worth the $ or time/effort. Mixing and smoking in a single bowl works best.
Side topic: I have a single bowl that does have a divider, effectively making it a split bowl - even this is hard to keep the heat right. It works, but it's easier to simply mix everything into 1 bowl.