How would this resolve the problem of people looking like clones? If Joe and Bob are both Fighters, and can't get a 20 in STR, then they're going to try to get as high as possible.
Even if it gave you points for point buy, making it easier to raise low scores than raise high ones, you still run into the problem that Fighters don't value Int, Wis or Cha. I mean sure, Joe could spend 2 point-buy points to raise his Wisdom...but...why would he? What incentive is there for him to raise that score?
You want to address issues with clones then the only solution is to increase the mathematical relevance of non-primary scores to classes.
I am surprised that you can't see how this would reduce the number of clones. I will try to help you understand why I think it would.
Joe and Bob are Fighters that choose not to invest all of their ASI's towards maxing out Strength because it is now more expensive. So, they might choose Feats instead, and most likely will choose different Feats. Let's say that they both prefer to boost lower Abilities instead of choosing a Feat. One might choose Wisdom to increase his Will save and his Perception skills, while the other might prefer to be tougher by increasing his Constitution, or to improve his ranged options with Dexterity. Maybe one of them styles themself as a leader of men and chooses to boost Charisma, and the other enjoys scholarly pursuits or wants to be a tactical genius so improves Intelligence.
And there ya go, greater diversity in builds. To me that is much more fun than both Joe and Bob being as strong as Ogres, and having no interesting choices beyond "Me swing sword again".