I haven't seen this suggested before, but I think it would be a valuable asset to half-elf players, and possibly open up some build ideas:
What if half-elf dilly opened up class skills to the player (with the exception of pick lock, disable traps, and other specific rogue skills).
So a half-elf with the rogue dilly could put no penalty points into UMD, or one with fighter could put no penalty points into intimidate, ect...
I don't see that this would be overpowering, and could be beneficial for those wanting to experiment with build ideas (intimiclerics, clerics that can actually jump , ect..)
Might encourage some creativity and make half-elfs interesting for some of the "fringe builds".