Do be aware that if you decide to return it to pressurized system, that hole left in the tank when removing the additional widget will need to be plugged very carefully, respecting the pressures seen in this system, which are quite a bit higher than many other systems.
The original tanks were constructed very sturdily for good reason, as if you calculate 40psi over the area of the tank, the force exerted on the walls is quite considerable, albeit well within the limits of the materials used.
Ideally the hole would be plugged from the inside, but that will be pretty much impossible without cutting the tank open. If patching from the outside, I would make the patch so it forms a ring around the circumference of the tube, like a strap and bonded in with solvent weld or modified acrylic. It won't be as pretty as a new tank, but won't cost much. You can use old PVC waste pipe for repair material.