By my rules Customization is used to bring your STR and AGl up to your modified current stat, so if you have a STR of 5(9), then you could Customize your limb up to that, and then add +3 STR on top of that, which still provides Cyberlimbs with the advantage of going above the +4 cap. In fact, my way allows for even greater upper limits, provided you have the other 'ware to match(Muscle Replacements, Muscle Augmentation/Toner, Etc).
But what about the idea of Hardening?
Current RAW in my opinion don't balance Bone Lacing with limbs. Plastic Bone Lacing deals unarmed DV STR+1P, which is MORE than a metal limb. Until you account for the increased STR. Strength being equal, I have a hard time accepting that a flesh hand with reinforced bones does MORE damage than a metal cybernetic limb.I dunno, maybe that evens out. But why invest all that money in a shiny new limb, if it's going to barely do more damage than your regular unarmed? Aside from Capacity for implant weapons and the bonus Condition Monitor box.
And yes, there is some room for abuse, but that is part of what I'm trying to find by asking here How abused could this be?. A human character with STR 4, Muscle Replecements 4, Aluminum Bone Lacing, and one Customized and Enhanced cyberarm would deal 10P unarmed damage, unless using his cyberarm, which does 9P RAW(Customized STR 6 +3 Enhancement), or by my rules does 13P(Customized to STR8, +3 Enhanced, +2 Hardening to match DV of Bone Lacing). A character with STR 6 or an Orc with 7 could then do DV 15 or 16. Ouch-but that same Orc could now get a limb with STR 3 for a LOT less, and wield a Katana or Combat Axe for STR+3 or +5, and do nearly the same damage, WITH AP. And my munchkin example certainly seems like a lot, but that uses up 6 Essence, and costs 187,500 y, with only the listed mods, no Armor, no AGL, which means Priority A or B. So yeah, he can punch like a sniper rifle, but that's about ALL he can do(Vs that Orc with one arm and an axe, who has a lot more Essence and Nuyen to spend).
And I don't believe in negating rules/nerfing rules for the sake of preventing such abuse(hate what they did to Critical Strike).