These I believe only had one oil line, right? They are sold as accumulators only and are basically used like an oil pressure shock absorber for lack of a better term.
The one I was checking out had oil literally going into and back out of it so the oil in the tank was used as added capacity and still controlled oil pressure fluctuations, I thought it was pretty cool.
I have one of the smaller Moroso Accumulators with a ball valve and a pressure guage, it's about the size of a fire extinguisher, but it only has a line coming off the bottom and it just holds "static oil" and the oil just goes back and forth.
Here is what my warped mind was thinking...

Build a three quart tank for oil with the diaphram deal going on at the top, have a coil of tubing running through the sump of the tank (making the total of external connections four) have an inlet oil pressure line, a feed line and a supply and return water line of say 1/2" tubing and have it thermostatically control oil temp and act as a pressure stabilizer, I think it would be the bomb for added capacity, oil pressure control and temp control in an endurance application...

GT
Just thinking out loud