The only thing I know to do is launch from PDVD directly, or possibly upgrade.
I know thats not the answer your looking for, but I do not know of another alternative to get WMC to playback BD in its original form.
Hopefully someone else can offer better advice.
If you like Power DVD, and WMC integration is important, it may be worth upgrading.
If you simply do not like Power DVD and want something else, the only other good BD playback softwareI know of right off hand are:
Arcsoft Total Media & Nero 10HD.
Arcsoft also offers a media center plug in.
Nero does NOT, so probably not a good choice.
So of the the 3, Cyberlink or Arcsoft will be the best bet.