Neil and Steve et al;
I appreciate your comments, though I am not the seer that dreamed of this.
...

The intention behind it could be to share tape drives without using a Library 
Manager, and to add TSM servers without buying more hardware.  Our TSM server 
databases and boot disk are on the SAN.  I'm confident the TSM/VM servers would 
be given the resources they needed.

One reasonable concern for building TSM servers on VM's would be that a 
virtualized server is not as stable as a physical server. Vmotion works most of 
the time. ESX hosts do crash, and if they lose their HBAs will take all their 
guests down with them. 

Best wishes,
Keith