Is there any reason a person on VDI couldn't host a LYNC meeting using LYNC audio?

That's a big question. 

With straight VDI, the audio would be sent from the VDI host to the terminal and the quality may not be the best, that said, if it works it works.

If the Lync VDI plugin is supported with your infrastructure, that would be a better option: https://www.microsoft.com/en-us/download/details.aspx?id=35457

If you can have the user call in via PSTN for audio, that would work as well.

The only real reason they couldn't is if it didn't work or the quality was too poor.  The best way to know is to test in your own environment.