I completely understand the the technical limitation mentioned. As an effective workaround, I wanted to point out GotVoice.com. I'm in no way affiliated with the company or service, but I did do a review of it and found it to be quite good. Essentially, it's an automated service that calls in to your VM, but it also can send you e-mails indicating you have a message and even embed an .mp3 of the VM in the e-mail, which saves you from calling in to your service. Additionally, you can subscribe via RSS to get your messages, which is very innovative. The basic service is free, with a limited number of VMs. I tested the Premium service at $9.95 a month and use it for both my Windows Mobile 5.0 Pocket PC Phone Edition as well as my Verizon home VM service.
Here's a link for those interested in my review. We even have a sample .mp3 VM so you can hear the sound quality, which is quite impressive!