I have one map where this would be nice, and I think your solution is the best I have heard so far.  Reasonably easy to understand.  Still is a bit random, but not as random.  It's not at the top of my priority list, but if Tom wants to implement it, my vote is yes.

SquintGnome - easiest way to put a xcel spreadsheet online is probably import it into google docs, and then post the link here.