I suppose one must first as, Why must one min-max the character? If your looking at points on a sheet, then I wonder if any Storyteller system will work.
IE: The points on the sheet, should reflect the person. It actually takes more work to go from the Master's to a PhD than it does to go from Bachelor's to Master's, or HSD to Bachelors..
In that I feel the xCurrent Level XP buy is reflexive of natural progression. Also, backed by the rule that you cannot buy from 0 to 4 in a skill with XP. You have to buy them all incrementally.
If I recall, as I don't have my books:
0 > 1 3pts
1+ 2xCurrent level
1 > 2 2
2 > 3 4
3 > 4 6
Now, pregame, what is the character? a Jack of all trades then yes, they should have a lot more points spread out and not min-maxed, a specialist will min-max. The backstory calls for it.
One modification that has proved successful in doing what I think you want, is to not only require the roleplay of working to improve a skill, but to add for a few players a 1 XP skill roleplay at the end of a session. The idea being that a player purposefully chooses and wants to increase a skill or such, goes out of their way to use or or in fact practice.. That should be rewarded.