In the past, the absolute maximum level of attributes a person could get was 10. No higher, no matter what you did.
You could have an attribute at 10, but when you wore something that gave additions to that attribute that would push it above 10 - usually armor or drugs - it wouldn't push.
So I ask for a way for that to be possible.
Why would anyone want to do this? Well first, it has more of a use for drugs, and a reason to face the addiction. Imagine having INT at 10, then wear a helmet that gives +1 INT and a drug that gives +1 INT. Now you have 12 INT. That would affect your experience gain, wouldn't it? Well what about Intellectual skills above 10?
There are 2 ways this can be handled:
Version 1 is that there will be additional perks you can choose at level up that are above 10. When you push your attribute above that level, those perks become live. If your attribute falls below that for some reason, then you loose it. At the same time, I think that if that makes you unable to use another perk that has a requirement of an attribute at a certain level, then you loose that perk till you fix it.
Version 2 is that there's just a note at the base of every attribute tree. For every +1 gained in this attribute above 10, gain X perk. That'd make it real hard to get above maybe +3 - 5 above 10, but it's possible with extreme effort, cost and even sacrifice