We do have a few folks that opt to use AD and GPO to manage the WSUS signing certs. Here are a couple of links that might be useful:
http://technet.microsoft.com/en-us/library/cc770315(WS.10).aspx
http://msdn.microsoft.com/en-us/library/bb902479(VS.85).aspx
A step-by-step guide for distributing the WSUS certificates via GPO is also available.
http://www.solarwinds.com/documentation/patchman/docs/Distributing%20the%20WSUS%20Publishers%20Self-Signed%20Certificate%20using%20Group%20Policy.pdf