Allow me to clarify something to make this a mostly moot discussion in the latter respect.
A CBM would work in a monkey. A cat. A dog. A whale. So long as the brain is as similar in function(which most brain parts are). A CBM will work on a mutation of just about any human mutant as well without much if any complication. Unless the mutant simply lacks a certain part of the brain entirely(brain damage?). Then it won’t matter at all, how mutated the person is.
While CBMs do not exist. The brain of most mammals do exist(despite my constant objection to this idea when I drive…). We have comparisons to a wide range of other animals to ourselves. So the real question would be. Why would humans make a CBM, DNA specific at all? This is of course rhetorical. Nobody making money off of them would do this. You would stuff one into just about anything and it would work. Never underestimate the power of greed.
Bio-electricity is the same in all beings. Electricity can change in size and shape/frequency. But anything so sophisticated as to be implanted generically into a wide range of humans could auto tune itself to just about any mammal. Insect and plant mutations…as long as you don’t change the brain. It should be functional. The mutation wouldn’t explicitly change the brain to make a physical change to something like skin or a leg or anything else. Like a person with 6 fingers on one hand. Your brain doesn’t change. You just learn to deal with another finger. Same signal FROM your brain. Just an extra digit.
The balance of a CBM system is still easier to go by frame size and to add modifiers of difficulty based upon mutations. As was mentioned here already. A toolkit in the hands when mutating into a paw/claw/tentacle etc… Would bork the toolkit. But apart from that. A limiting factor should also be like that getting zapped idea too. Too much crap in your body that conducts electricity can up the electric damage to fry you almost instantly. Most/more CBMs = higher the percentage of being captain crispy.
Another limiter is how many batteries should be allowed in your body. You can even argue hosting a CBM exo frame to house your batteries. Allowing more internal CBMs while being able to have batteries outside and swap-able. Humans have at this time in real life bionics that do this. A woman has an implant attached to her brain to allow her to see depth via lights. Which require external batteries.
Tattoo circuitry to make Tattoo digital time telling bionic(a standard digital watch). It runs off of blood flowing or heat depending on the method of choice, as the time device require almost no electricity to function. Programmable image tattoo. Same method as the watch for power and it can be programmed to change the capsule(like a tv pixel) under the skin to change in a specific order to show a different image.
Reference sake type into google:
Monash implant, vision implant onto the brain for vision, electronic sub-dermal tattoo. The tattoo variants don’t even require a brain. You can using a radio signal like wifi or bluetooth or something similar.