No, there's not really any way to do that, as it would wreck past accounting.  It's actually a fundamental design issue (perhaps you could call it a flaw) suffered by most pools that use the worker paradigm.  I could possibly hide them permanently, but then you couldn't recreate a worker with that same name.

cuz - if you turned off your workers now, you'd still receive payments for the next ~7 blocks, which would recoup your 23%.  Does that answer your question or do you still have questions about it?  We had a fairly lengthy discussion of DGM several pages ago in this thread that might help clear things up, as well... but I will be happy to answer any additional questions.