How about a 3rd tier implants, requiring LV50, and 1per character limit?
The implants will basically be another "perk", where each implant is simply named after the perk itself.
For example:
Stonewall Implants, Lifegiver Implants, etc
In order for the bonus to take place, you must meet all the prerequisite (such as LV requirements, skill requirements), or perk is disabled until you reach the skills or the LV.
If these implants were to become not super-hard to obtain, it might create a diverse and interesting trading environment for the community, since there will be so many different kind of implants now (same as # of perks).