Depending on the plumbing run lengths and height of the scupper above the intake, you'd be better off using a waterfall style pump (high volume flow rates at low pressure) than anything like a whisperflo pump which is a high-head (high pressure) pump. Waterfall pumps are also significantly cheaper than standard, single-speed pool pumps. This is an example of what I'm talking about -
http://www.pentairpool.com/products/pumps-inground-waterfall-specialty-pumps-191.htm
In this type of setup, you put your scuppers on a completely separate plumbing loop. There would two, anti-vortex wall drains which feed the suction-side of the pump. The pressure side of the pump is then plumbed to the scuppers. You can add separate shut-off valves to each scupper if you want to be able to control or fine-tune flow. The thing about waterfall pumps is that they are low head and can only draw water up a maximum distance before they lose flow. Typically, the maximum draw height is 10' or so. So that means the wall drains must not be 10' lower than the scuppers. All waterfall pumps will have a pump curve or specs showing their flow rates as a function of draw height. SO you need to match the flow rate of the waterfall pump with the sum of all the flow rates for each scupper. Example - if each scupper has a design flow rate of 25GPM and you have three scuppers, then your pump has to supply a minimum of 75GPM (100GPM to be safe) to satisfy all the scuppers.
This isn't rocket science but it seems to me that most PBs don't take the time to think about it and just slap an oversized pool pump on anything they can without regard to proper plumbing and water flow. Proper use of a waterfall pump will also save you money as it puts less strain on your pool pump and you can run the scuppers with a more efficient pump.