What if you gave each race an assignable +2 in addition to their two static scores, while decreasing the points available for point-buy? So humans get +2 to any two stats, Elves get +2 to Dex, Wis, and any one other, etc. (No stacking the racial bonuses!) Then, decrease the points available during character generation -- say, an 18-point buy.
In this fashion, every race can achieve an 18 or 20 in a stat for the same price as any other (buy it up to 16, then get a +2 racial bonus -- either a fixed bonus or an assignable bonus). The sliding-scale for point-buy still discourages high scores, but no race has too strong of an advantage in any one class, because everybody can achieve a high score in the crucial primary attack modifier for the same price.
The more I think about this, the more I like it. It is a little complicated, but preserves racial advantages without discouraging uncommon race/class combos.
-- 77IM