That is why I said 'impossible' (notice the single quotes), there is no game logic to stop you but I would personally not do it and instead follow some kind of role play that makes PDCs missile/hangar/troops only.
Or, you could concoct some kind of handwavium TN mumbojumbo that allows Mesons to fire through the crust without any side of effects on the firing mechanism.
I guess what I am trying to get at is that your projector for the meson cannon might possibly have to point through your actual PDC inorder to hit the PDC on the other side of the planet. And to me, that is not a good thing