VMware has proposed an open standard for the format of virtual disk images (see http://www.vmware.com/interfaces/ for additional info). Support for this format in Parallels Workstation would offer users access to the growing number of "virtual appliances" (see http://www.vmware.com/vmtn/appliances/index.html for additional info) which could be installed and run in Parallels Workstation. This would mean shorter install/config times for predefined functional VMs, attracting more Mac users to Parallels, and possibly drawing users who might otherwise purchase VMware Workstation (those of us who work in multiple host OS environments like having a single toolset that operates across all platforms).
This would be a great feature, especially since other parties are now releasing software as VMware images (like Zimbra). It would be great to be able to transfer images to/from VMware Server on my server and Parallels on my Mac.
Maybe you should tell VMware to support the Mac. They've been around for years and have turned their back on the Mac, and now you want Parallels to do something to support them. Many Mac users have never been exposed to the world outside of their confined environment. Projecting that world onto the real world is going to be a reality rush.
Diane Greene, the CEO of VMware, has admitted on the record they have at least one of VMware's products running on Macs in their labs (I'd guess VMware Workstation, but that's just a guess). See this article for information.