Good questions about the licensing angle. I will look forward to the responses.
I also want to say this post is clear and helpful. I wanted to mention something that has been an issue in the past for me. When someone says that a stand-alone physical processor's utilization rate is 25 percent, it really begs the question: is this 25 percent at peak periods or is the 25 percent averaged over a period of time? If averaged, the we have a problem. You can consolidate these physical servers as guests on a VM host. But when the peak period comes along, you might miss your SLAs by a large margin. That is, if all the guests have peak periods at the same time, you might be over committed to the point of having excessive processor pressure.
We also forget that there is more to the story of consolidation than just the CPU utilization (peak or otherwise). There is memory and there is I/O. Database applications aren't always consistent in CPU, memory, and I/O. Some can be high I/O and low CPU, others can be high CPU and low I/O. So App_A might use half the CPU of App_B, but App_A might use twice the I/O of App_B. This might balance out until the VM guest for App_C comes in and is similar in design to App_A. While the CPU utilization is better than hoped for, we will find the applications running on the VM host are running too slow.
For the DBA and VM admin involved, it behooves both of them to ensure there are good performance metrics gathered before committing to a particular VM architecture.