Are you still going to participate in PMS (ie upload your Mencoder builds, fixes, enhancements to git/Google Code)? If not, should PMS just be abandoned and have all the contributors/coders work on your version? I foresee at some point that the UMS and PMS code bases are going to grow apart so much that they are no longer going to be compatible (ie a fix for one version may not be necessary or work for the other version).
Personally, I don't mind abandoning PMS in favor of UMS, but is your code going to open source as well? Is it in git? It obviously isn't using Google code because your latest version of Mencoder is in UMS but not uploaded to Google.