Some of the peristaltic pumps are painfully slow, leading to long dive times. The Welman shouldn't need a large dive tank if the conning tower is freeflood, but all the same, I wouldn't go for anything too ponderous.
The Neptune pump has a fairly good flow rate. Not sure about efficiency though mind you- the pump is directly driven, and as I recall relies on slippage of the motor spindle to slow it down.
An alternative is to use the switcher, ballast bag and pressure switch, but use a small geared pump instead. With a bag system the pump is working against very low pressures, which helps the life of the pump. These will give you a good flow rate, but are not self sealing, so you will need to make a pinch valve or fit a solenoid controlled valve. Pinch valve is easy to make and cheap.