Extra punch for my space marine command squad

In my Imperial Fist army I run Lysander with a command squad in a drop pod. The squad is equipped with 2x power fists and 4x storm shields. I like the unit because it stops hammer units dead in their tracks even if it is a little expensive (it is also a loadout consistent with my army's fluff).

Recently my opponents have switched from assaulting or concentrate anti-tank firepower on the squad to unloading with bolters and autocannons. the army can survive for a while but it just isn't equipped to dance around with other troops. I am looking for something to add to the unit to increase the firepower. Hopefully it will be big enough that my opponents have no choice but to take some big hits or try to lock the squad in melee. Some of my thoughts were:

• swapping bolters for plasma guns
• swaping bolters for meltaguns
• adding a chapter master for orbital bombardment
• adding a master of the forge with a conversion beamer
• adding a librarian with vortex of doom or smite

Any thoughts? Anything you have done that worked really well.

Thanks,

Rix