(Not an engineer either) My understanding is that it's been done before on smaller scales but having a giant piston in the tank requires a good seal, railings to keep it straight, and overall way too much mass and rigidity. Consider that the tank walls are only a few millimeters thick.
Instead, it's more common to use gasses injected at the top of the tank to push the liquid to the bottom. Falcon 9 uses helium. Starship uses https://en.wikipedia.org/wiki/Autogenous_pressurization as well as small header tanks for the landing propellants.
Instead, it's more common to use gasses injected at the top of the tank to push the liquid to the bottom. Falcon 9 uses helium. Starship uses https://en.wikipedia.org/wiki/Autogenous_pressurization as well as small header tanks for the landing propellants.