The worst idea to implement in that above example would to give that player with 110+ in each stat 20 extra ability points. It completely removes any need for diversity in builds, as you would literally be able to take all abilities and passives. That would remove any risk or calculation in making a build.
*in Javik voice* Wut tis dis risk and calculation that you speak of, human?
Not all passives have a general effect but are limited to a prerequisite skill. Players are also still limited to 4 abilities as well. So diversity still exists in that regard. Leveling would still be encouraged, especially after someone has nerf their stats back into noobdom. It's not as if having all abilities will allow a player to run roughshod on the game (100/100/100 promo stats does though).
Something to also consider is incremental trade usage.
First time use: 5 pts per stat
Second time use: 10 pts per stat
Third time use: 15 pts per stat
... and so forth. After 5 uses, someone with 100/100/100 stats would noobie all over again. A table could be designed low enough for the average players to want to use it but high enough at the top-end to discourage the over-achievers.