As the OP's questions have been answered, I guess it's ok to go off topic now...
I agree with All4BigGuns on this one. I know it's RAW, but this rule allows players to deliberately dump stat STR and AGL, knowing they can cheese up an arm or two to compensate. The fact that arms don't affect limits is nothing but the barest nod to balance.
I also strongly, vehemently, disagree that maxed out limbs are an 'integral part of the chromed street sam build'. The only people who make that claim are the same ones who think there is only way to build each archetype, with carefully min/maxed stats. All their characters end up as carbon copy clones of each other. Does 'carbon copy' even make sense anymore? Why not 'cut and paste' clones of each other... yeah, I like that better. My point is, I don't think every street sam should have Wired Reflexes II, Muscle Replacement II, and two maxed out cyberlimbs; they all carry an Ares Alpha and an Ares Predator, wear an Armored Jacket with Helmet. Show some creativity! There are plenty of perfectly effective builds that don't rely on maxed out limbs to be effective. Well, unless you consider anything less than maximum ineffective.
The point of cyberarms is to increase your stats, yes, but not to allow stat dumping.
In my opinion, cyberarms should only Customize up to your current stat, be that 4 or 6(9). I think they need to be tailored to suit your frame, not grossly exceed it. Once you've Customized them, THEN you can Enhance on top of that. My was allows for a much higher upper end build(for those cheese STR6 Muscle Replacement III Cut-And-Paste street sams, but eliminates the stat dumping AGL 1(9) cheese. And since cost seems to be the only real limiting factor on cuberarms, my way requires a lot of resources to get into the top tier stats, as you need both Muscle Replacement or similar ware, AND Customization.