Humble opinion of myself.
The particle cannon should be twisted to be able to attack fleets stationed in raid colonies (only in that occasions. To normal planets just defenses)
Once you get one created next to your planet, and you have no ways of magically generate X amounts of phoenixs, you are doomed to an eternal escape flight + shutdown production (or transport them to a very far colony) or to go into vacation mode.
If you get besieged by a player that has x2 - x3 points than you, its over. Its a cake for the other player (or players).
Have a nice game!