Seeing a metachrosis idea pop up recently, it got me thinking about how logically, having less limbs with skin sort of makes it harder for metachrosis to do its thing. I don't know if this is how it actually pans out in game, though logically you'd assume that it'd impact it.
Anyway, the idea is simple: a cyberlimb coating that has a togglable or permanently-active component that essentially replicates the effect of metachrosis. It'd impose additional CPU load that you could address via a dedicated coprocessor (if you're feeling generous, you could just fold it into the existing mobility coprocessor), or just tanking it with an overclock, and you'd be able to turn it on and off with a cyberware command.
Since this'd be a coating, you'd be able to apply it to any piece of outwardly facing customizable chrome, which would allow you to get pretty good but not complete coverage. Metachrosis would be enormously cheaper than doing this.
SPLATJOB