CSA's Believe It Or Not!
Were all the mounts checked for debris in addition to condition, in particular the rear engine roll restrictor (mount) ? It could be worth a second look.
Automan, Ford says that some 2000-2007 Focus models have "excessive engine vibration" at idle. They have issued Technical Service Bulletins and revisions regarding this.
They say it is caused by small stones, road debris, or snow and ice becoming packed in the rear engine roll restrictor. The fix is to clean it out and the way to keep it from coming back is to install a "service shield" (Ford part # 2M5Z-16102-AA).
A cross member-to-roll restrictor bolt must be removed, the shield put in place and the bolt replaced to hold the shield.
It doesn't sound like rocket science. Check with your friendly Ford parts guys/gals.