MultiValueControl field rules and Web client

Hi, I've been working on clearing fields when users clone work items. MultiValueControls don't seem to play nicely with <EMPTY /> (which appears to be by design or at least known) so, I found a good work-around that uses <COPY from="value=" value="" />, which plays nicely with the IDE client (in that everything is functional and appears to work as intended), but the web client no longer shows any drop down box or values when copying "" into the field. From an end user perspective, it looks like a weird failure. Any guidance?