Remember you have no constant flow so the pressure will equalise. A restrictive device might get you there but the loop would have to flow under pressure all the time. Otherwise just a delay in reaching pressure and a slow bleedoff would result. Very slowed up response to what was occuring.
From my limited search so far pressure devices are quite a big buisiness in the industrial realm. Generally as they are sold you can pay big dollars for a self adjustable one. Or have them custom calibrated in special orders. Cheaper is the operative word for these.
The second item is the operational enviroment to consider. Oil gets hot and the device must be happy at 120 pounds pressure load as well. Sensor cycle reliability has to be well beyond usage profiles. ..I do not think american engines have the bypass pressure set as high in the oil pump either. Or more likely the american oil pumps have generally been of lower volume designs. Generally mercedes survives at high speed by paying attention to their oiling system designs.
There seems to be no other valid so called standard pressure device except the automotive ones at down around five pounds. I too think they are not ideal. Yet far better than nothing.
If your pressure is dropping you want the sensor to get the message as soon as possible. So as little restriction as possible. Time is of the essence here. If your oil level is getting pretty low and you take a corner you might get a beep for example. The oil gauge has too much inertia to preform this function usually. Or the event goes unoticed. As little delay in the system is important to assure this feature as well.
As soon as you go upwards in pressure past ten pounds the switch opens. Since this is a custom deal I would really preffer to calibrate it at 1 bar or about 14 lbs. There are some tired engines out there though. So I will try 10lbs and test it to make sure it is not too high for the average 123 car. I am pretty sure it will cover more than 90 percent of them.
Just gives perhaps a little more time in event of a failure if a higher pressure switch is used. Depending on the severity of the leak or problem of course.
In most cases it will save your engine. It is not just the oil coolant hoses to fear. A sudden motor oil leak anywhere on a trip could do you in. A lot of engines have been damaged by the oil change plug not being tightened over the years alone. Or blowing an oil filter off. Even just leaving the oil fill cap off. The second example is not a concern on 123s. It would take dynamite. Yet you could still develop an oil filter container seal leak suddenly.
For the high or overheating temp I will make it customer adjustable though. Or this is the thought now. It will probably land up working off of the present temp gauge sender. That is a little down the road though at present. Simple as possible consistant with not being a pain in the posterior. I am determined to do it properly. Otherwise my remaining life might be spent answering emails.
No return price quote on the 100 sensors yet. I hope they are sharpening their pencils. If I can just get an oem price we are away to the races. Keep the ideals coming. All viewpoints are worth examining by everybody.

The only advantage I have if it is one. I have owned multiple diesels with these devices..Most where more sophisticated. Believe me when I say they do their job and earn their keep.