My general rule of thumb is to no do anything that would cause Disney to re-think their policy or clamp down on existing rules. It is a nice benefit that this is permitted. I would not want to be the one that ruins it for others. That is why I generally keep my outside beverages low key.
Also, I know drink prices are high, but that does not necessarily translate to lots of money for the hard-working pool staff. I try to order some food from them or a unique drink supplemented by my own food/beverages. They work pretty hard and I appreciate the service they provide.
Yeah, my plan is not to bring in a huge beer cooler and sell them to other customers. We do plan to order an appetizer by the pool and such, but are just looking for one or two drinks by the pool while we relax