We need 1 more headless hammer handle to craft a catapult of our own (with medics already doing that its probably not necessary), we have an action free otherwise.
Also, medics should probably attempt to place the catapult in N14, in case it has to be placed and is based on line of sight (and can see diagonally) and the projectile has a travel time. Maybe, just maybe, if you have an action 7 and it does not actually have to be placed, CO will look past it and allow the 7th action rather than dismissing it as failed action.