Did you ever get anywhere with this? I need exactly the same, we have two Virtual centers in India that we'd like to merge. I was thinking about just copying attributes from one SQL table to another. Is that way too simple?
No you cannot merge two vCenter servers into one. You would have to migrate the hosts and settings from one environment into the other.
The only other solution I can think of is to use linked mode so that you get a single view of your two vCenter environments.
Long term I would just wait until vSphere 5 comes out later this year and use that as an excuse to migrate both environments into a newer better vSphere 5 system.
They are linked, I have several virtual centers linked. The reason for consolidating the two virtual centers in India was due to maintenance renewals. If I powered down both virtual centers and wrote a SQL script to copy and insert the data from one database to the other, you don't think that would work?
I was interested to see if someone had come up with a manual or scripted process for this as I have needed to do this several times myself and I found the following;
You could do a full scripted backup of one environment and then import it into another.
I basically managed to achieve this with a powercli script, that exported everything contained in one VC to the other.
There if you like to know more, it worked very well