Trying to plan a pressure-tank + air compressor for raising home water pressure
Offer, I do not know of a regulator that will do what you want but it could be done with solenoid valves.
You discuss a 200L pressure tank this is 52.8 gallons
Even with low flow shower heads that’s not much shower time. my wife 3 daughters, 6 granddaughters would think that is just about right for 1 shower.
(A 2.5 gallon shower head for ~20 minutes).
You state that electricity is not reliable, but air compressors also use electricity and as someone that has cheap small volume air compressors to high volume compressors these are energy hogs they are not an efficient way to boost your pressure.
A pressure tank is usually used to provide a buffer to the system and reduce the start cycles on the pump.
It is obvious you do not want to hear this advice and I will accept the down votes but air over water in a dynamic system will be more costly and more prone to failure.
Just as an example I can give dozens of water pump designs used in hundreds of millions of homes but not one example like yours.
Could your idea work, sure it could, but it would require an air compressor and solenoid valves to control the tank pressure for a very limited amount of water between recharge cycles.
A small pump 1/2 horse power possibly smaller could provide the flow &amp; pressure from a holding tank. This is what people in the US do when they have low flow water wells, they pump into a open cistern or tank not pressurized, a pump at the tank pressurizes the system usually comprised of a small pressure tank to reduce the start cycles. A large plastic tank to hold water is not very expensive.
I live in a zone that has abundant ground water. There are some areas that the water is deep or they don’t have a good flow so a holding tank or cistern is used not air over water.
It is a good question and I up vote it for that but I do not think it is economically viable.