I would be interested in doing this, however I don't currently have the time to do a complete test.
I'm in Colorado until the end of the month and once I get back to Canada I'll be working on the asset allocation module for Automatic Investor.
However I will run an initial batch of tests in February to see if your idea works. If it looks promising I'll make some time to run more thorough tests.
BTW, did you come up with this through a logical thought process (such as Matt's MattMod) or did you simply wonder what would happen? Either way, I think the idea is worth a look.