In addition to my original obligation issues, one of my players is very interested in getting his vehicle equipped with a blaster weapon. He did this in another game we were in (we were both players), and the weapon he got did starship scale damage, that ended up blowing through everything, and we ended up stopping the game because it became less fun for the GM, and he didnt want to arbitrarily get rid of the weapon or taise the difficulty to much for the rest of us.
Now that I'm GMing, how should I go about his request? Can i substitute the big guns for player scale ones?