Bear with me if any of these are on the to-do list, or already exist in some form and I just haven’t noticed.
First, EMP effects, grenades and the bionic. It should have a chance of shutting down robotic enemies on death, killing them without making them explode. Less collateral damage this way, for the player and surrounding items.
The ability to unbind bionics. I figure this one is probably on the list, but in the meantime, would it be possible to implement the option to disable the automatic assignment of letters to passive bionics? I think this would be a good “band-aid” for the problem of having more bionics than we have keys to assign them to.
A “hold breath” key. It would rapidly drain stamina and cause temporary severe mouth encumbrance, so you couldn’t (or wouldn’t want to) sustain it for more than a few turns at a time. But you would be able to minimize or eliminate momentary some smoke and gas damage. Like, you’re fighting enemies in a doorway and a bloated zombie sneaks up behind you. You’d hold your breath for the three or four tiles so you could get out of the gas without damage. You wouldn’t be able to just hold your breath and keep fighting.
Since strength sort of doubles as the “endurance” stat, perhaps a high strength could allow you to hold your breath longer.
The ability to “attach” your Power Armor Interface bionic to a suit of power armor, so they activate and deactivate at the same time, or at least within a turn of each other.
The ability to convert power armors to the other weights of power armor through the recipe menu, using a very high mechanics and electronics skill (at least ten). Converting lighter to heavier would require some superalloy plating, electronic scraps, copper wires, et cetera. Going from heavy to light would produce these as by-products. This could actually be a mod, if anyone cared to make it. It sounds pretty easy.
Last, and most complicated. Modular power armor. Remove the electric insulation, climate control, and rad protection from power armor by default, and make them optional modules that you could find and install yourself, similar to gun modification. (You would be able to find pre-modded suits with one or more modules already installed.) Other modules would be found in military bunkers and bank vaults.
Example modules: (Stat)+1, Speed+5%, a module that enables a melee style similar to the Close-Quarters Combat CBM, night vision/infrared vision, air filtration (for gas or water), a configurable auto-injection module for morphine, RX11 stimulants or RX12 ampoules, headlamps, integrated blades, sealant for underwater movement. Using the armor with the ‘a’ key would bring up its context menu with a list of its modules, allowing the player to toggle them or activate them.
Some would be considered “head” modules, like headlamps, gas filters, and alternate vision modes, and would be installed into helmets. Others would be “body” modules, like radiation shielding or electrical insulation, and be installed into suits themselves.
Some would require power, others would be always-on (like filtration and insulation).
On a last note, each one would increase the weight of the suit a little or increase its power drain when active.