A fun thought I had
in the middle of a "Tony Stark" playthrough.
Weaponry built into the arms of power armor. Lasers, missile/grenade launchers, machine guns and the like. Maybe even giant laser cannons or missile salvos built into the torso armor, if one would wanna go crazy.
I dunno enough about modding to know what would be the easiest/cleanest/most intuitive/not impossible implementation, with or without F4SE, or waiting for the GECK.
My ideal implementation would be craftable mods for arms/torso that add the weapons to the power armor's inventory. Weapons that stick with the power armor itself, like the armor does.
If you could unequip the weapon but have it remain locked to the power armor's inventory, it wouldn't lock you from using other weapons or your fists.
Some weapons could be tied to the grenade equip slot, E.G. the torso armor weapons, though I can only hope that F4 modding is open enough to allow this.