So I see what you are trying to achieve, and your approach can be moddelled yet you will need to really know what you are doing if you want to start transferring entities in and out of queue's, as well as adjusting capacity of vehicles to circumvent default routing logic.
Alternatively, I would set the Retailer capacities back to one and treat an entity as a shipment from the warehouse to a retailer. I would also look at add a material element to the transporter and each server and utilize Simio's produce and consume functionality to drive variation in supply and demand.
This will allow you to utilize the base functionality of the transporters, without dabbling in capacitative resource allocation, unless you fully understand the intricacies of the inner workings of a transporter. Task Sequences embedded within the servers should allow you to easily accomplish your objective (basis production and consumption of material), without needing to utilize process logic and corresponding Produce and Consume Blocks.
Hope this Helps.