I haven’t read the whole discussion, but as I was reading I was expecting this discussion to go a different way : CBMs can get damaged. That’s one way of getting around the “one time fee” of CBMs. I would think it makes sense that if a hulk smashes you in the chest, that maybe your internal furnace wouldn’t function like it used to. Getting hit in the eyes might scratch or damage those diamond or IR augmentations.
Repairing CBMs could be as easy as having the tools, time and product, pop open the bionics menu, and hit the repair key. It could be as difficult as removing the CBMs and repairing and then reinstalling it.
Perhaps even a new CBM could be installed, a CBM Shielding, which would absord the damage or mitigate it or something (although this is moving away from the goal of having maintainable CBMs). Other CBMs could withstand the abuse, like the military grade CQ combat ones.
I would think programming wise it would be as straightfoward as adding a bodypart to the CBM, a damage tracking integer, some code that damages the CBM when you get hit, and then the repair key in the bionics menu. CBMs could either behave differently while damaged (requires time to code) or they could simply fail to turn on, costing time, or turn off automatically like a misfiring gun, or consume more power, or cause any number of effects that the “failed CBMs” already do, like pain and noise.