Understood. You would need some kind of rig that lets you dispense without removing the cap. Threw this together with a few things I happened to have lying around.Getting the volumes and keeping the volumes are very different. Once the cap is removed and the first bubble forms, you've got a nucleation point chain reaction.
And before anyone asks - I have absolutely no intention of testing this at 100 psi.
Edit - the pictured tap is only rated for 20 psi, so that's at least one thing that would have to change; might want to add a carbonation stone too, and there may not be room to snake another piece of tubing thru the cap.