I've had a love/hate thing for cyber limbs for a long while now. I love them for the ambiance they provide the setting... I hate tthem for the munchkin abuses they can bring in (the 1/9 agility, the armor, etc).
I have used house rules in the past....
Removed mods from them...
Banned them except for fluff... (want a metal arm?? ok you got one! same stats as your reg arm...but no money spent)
For 5e I said "WTF, take them as is and see what happens. "
and so far, they haven't been more then an annoyance at best, a detriment to the player at worse..... Yea the extra armor makes them soak more... but big deal, just means they fall down 2 rounds later (or a round earlier in the case of the "tank".... Told you 1 WILL was a bad idea...)
yea the arm with 9 agility makes them shoot that pistol really good.... but does nothing for almost all other tests... or at least tests that require more then your arm....
all said, I feel arms are mostly balanced... well as balanced as a robot limb in a setting that also has dragons and magic can be, especially considering the cash and essence costs.
And really, those 2 things are the biggest parts for the equation of balance (other then the fact that, you know, your are missing a freaking LIMB!). For the cash and the essence costs of a cyber limb, the player could have gotten a whole other piece of ware that could have been equally as good (or several smaller combinations). However, unlike other cyberware, a limb is a freaking large piece of meat to cut out!
Don't want that datajack any more? No problem, the doc can cut it out and stich the wound closed.. in and out in 5 minutes! (ok well not really, but you catch my drift)
Want to replace your wired reflexes with a synaptic booster? Sure, yank out the wired, throw in the SB and away you go! you even have an essence hole for the next upgrade!
Tired of your cyberleg? No problem! just rip that mother off and hop to your next job!!! Now you really do resemble a "Gun Bunny"! (so wear the swimsuit damn it!)
I mean, until Vat grown limbs come back (if they ever do, what with the nano problems), a character that takes a cyber limb is making a final change to their character that they can't walk away from if they end up unhappy with their choice (in the case of a cyber leg, literally!)