Another thought for you, this time on a new Wealth stat:
Your Chrome score summarizes your transition away from the flesh to the technological. As your Chrome increases, so does the amount and complexity of your cybernetics, as well as your distance from the unaugmented. Your Chrome score may ordinarily never be higher than your Prudence+1, and you may only purchase Chrome if you have the cybernetics interest.
Additional Prizes: This is the number of additional prizes you may hold, provided they are in the form of a cybernetic upgrade.
Error Range: While the use of cybernetics is increasing, it is a sad fact that some people respond poorly to visible prosthetics. Each time you make a Charisma-based skill check targeting another character, your error range increases by this amount when your Chrome score exceeds the target's Wisdom modifier or they do not share your cybernetics interest.
Mr. A hits on a really important subject here: resources.
SR3 has two issues (or features, depending on how you look at it):
1) The character creation system does not necessarily make characters of equal power level. A maxed out Mage or Million-dollar samurai are a lot more capable than, say, the investigator or the ganger.
2) It is absolutely possible for characters to start out with more nuyen worth of cyberware in their body than they will ever make again. Standard Shadowrun adventures often list contract ranges in the 10,000-20,000 nuyen range, sometimes up to 50k. Depending on how many of the special rules you use, this kind of cash is barely enough to maintain and repair cyberware and lifestyle, nevermind upgrade (especially if you add the implant costs).
One of the strengths of FC is that you can handle all this with levels and level (no pun intended) the playing field. But that means that resources that usually cost cash have to be coupled to level somehow.
I think the basic reputation and prize system works for "incidental" cyberware (like eyes and other cheap stuff). I think that there should be some option (maybe a specialty?) that allows you to boost up your resources for buying 'wares, eg:
Specialty: Street Samurai
You are the chromed up predator of the Sprawl.
Bonus Feat: Chromed
Heavily cybered: any time you receive a bonus feat, you may take Chromed instead.
This feat may be purchased multiple times. When you purchase this feat you gain 30 renown points that you may spend on cyberware prizes. The limit of prizes you may hold increases by 1.
A comparable specialty could be made for deckers and riggers, only in their case, they get to spend the rep on decks/software or vehicles/drones.
The Essence attribute should be integrated then as well. Essence could be stacked up straight from the source numbers, or it can be calculated from the renown points for balance. The resulting number should be added as a penalty to all Medicine checks targeting the character, as well as spells. I'd have to dig deeper into the source material again to see if resistance to diseases and the like are also affected.
I wouldn't have Essence affect social reaction to the character, since you can fully chrome up and still look very human if you put down enough nuyen.
Has anybody tried to calculate the costs for some standard items? Here are my attempts:
+2 to hit for ranged attacks (smart-linked guns only)
Lesser Charm, Accuracy Bonus, rep cost: 16
+1 to Dex and ST per level
Lesser Charm, Attribute bonus, rep cost: 20/level, max level 4
+2 Init and +1 half action per level, max level 3
Spell Effect: Haste (sort of), item level 5, rep cost: 6/15/30
Those look like some pretty high prices. Either the power level of the cyber has to be toned down, or Chromed has to provide a lot of rep.