This is a known issue and there's a workaround posted here:
edit: Please note that the workaround isn't a supported one by either Microsoft or VMware, but as you mentioned having looked for a workaround, figured I might point you to that post.
Wil| Author of Vimalin. The VMware Fusion Backup app |
| More info at http://www.vimalin.com |
| Twitter @wilva |
| Wiki at http://www.vi-toolkit.com |
| http://www.vimalin.com/why-is-time-machine-not-a-good-backup-for-virtual-machines/ |