In one of the DLCs, please add the ability to obtain a back-mounted TX-28 MicroFusion Pack for use with power armor so we don't have to be tethered to fusion cells and don't have to worry about running out of power in the middle of combat. The increased power output of the microfusion pack should also increase strength and negate any speed and agility penalties. In other words, with the microfusion pack you should be able to move while wearing power armor as quickly as you would not wearing power armor. Since all armor is now based on the same frame, this should apply to all power armor.
It would also be great to add the ability to chemically harden power armor pieces, increasing resistance to all forms of damage to the point that we can ignore anything less than energy weapons and heavy kinetic weapons. If a few raiders can catch you in a crossfire and whittle your armor's HP to nothing with just machine guns, what's the point of power armor?
Of course, these upgrades wouldn't come easily so I'd expect a supremely awesome storyline to go with them.