You could use managers for the production, you just need one of each potion you want in a manager under the brewer that is using it, a manager on top of each brewer providing a stack (or so) of the ingredient it needs, and a manager set to accept all potions in the system will brew (from water bottles to the finished product), set on the lowest pecking order (so if your managers serving the brewers are set to 2, you put the one on the result/ intermediate chest on 1(or 3, but I'm pretty sure it's 1)), and voila, auto brewing potions using redpower managers and tubes. Not including the power and inputs, the brewing system will occupy a 2x2x5 area for a 4 stage potion