The unit canon is a very impressive bulding however i think it is better suited as an orbital building for following reasons: 1.Realism. It is more logical these drop pods are fired from space rather then be launched from a planet. 2.possabilities. naval planets have a hard time getting an assault army together this would help them since unit canons are not buildable on water. -same goes for gas planets, they can become more interesting with this feature. 3.Less sudden assassination. this can be worth of discussions but unit cannons are quite capable of assasssinating enemy commanders with little awareness. If these structures are placed in space then you know what an enemy is planning and the intel wars experience greatly increases rather then now "oh damn i forgot about those" for the casual player.