I have a couple relatively uncomplex ideas for keeping the Lucifer cannon potent (as it should be), but a little bit more regulated:
1) Charge some small credit fee for lucifer ammo (or any energy weapon for that matter) refills. Keeps people from needlessly spamming the entrances, but if made cheap enough, really doesn't impact any other aspects of the weapon.
2) Make the Lucifer cannon actually do a moderate amount of self-damage! It's horrible being a dretch and finally getting close to somebody with only light armor/helmet on, only to have them blast at their feet or at a nearby wall, killing you but taking very little self-damage