When blueprints were first introduced (late in 2238), they were very rare, hard to find. Very cool feature but over time their presence in the game evolved. Now, we can buy them. In fact, when i go locker hunting, i find blueprints at a rate that feels fair - i think it is well-balanced now with Reloaded's changes.
And when i hunt lockers, i very rarely find oil cans, less common than blueprints.
So i suggest looking at implants the other way around; consider this great new feature to be somewhat similar to blueprints, which evolved into an item that, while still rare, can be found at a fair rate over time with enough effort. Consider adding implants to random lockers to be found as rarely as oil cans. In all this time of playing, i have only found 18 oil cans and that is after a TON of intense searching for blueprints. If i had found 18 implants by now, i would still not have enough of them; i would still be avidly hunting in need of more (for multiple characters), but at least i would have some and probably a few characters fully upgraded.
As it is now though, their rarity seems too intense. I have never once found one. I have only 2, and this is after gaining over 10 million combined experience points of play time: 1 was purchased via player trade, and 1 was given to me as a gift!
So as it goes with all new, cool features, time tells the tale of balance. This part of the story is a sad, slow struggle just to get enough implants for a single fighter. I suggest upping implant findability. Keep them non-purchasable, but add to random lockers, more rare than blueprints (like oil cans). This is how our current implant-unfairness can be softened a little bit. The big gangs will still have more (via TC) but any solo player can get there with enough time and effort. Otherwise, the chasm between newer/soloish players and the big gangs will remain too wide.