Multi Domain Certificate - Experience

I have a hosted solution (software as a service) where I allow each of my customer to have their own unique domain name. I did a lot of research and realized that Multi-Domain Certificate was the best solution for me and went ahead and bought this. And this works great for the url’s that I have already installed.
The issue is as when I keep adding new customers - I have to replace the certificate and get a new one which includes the new domain name along with all my existing customers. Right now I have 10 customers but looks like very soon it will be more than 50.
Every time I replace the certificate - the comodo staff treat it as a new request and restarts their doc validation process all over again - For each new domain that I add - I have to open support tickets - get into a call - explain the whole thing all over again that only 1 domain is new - the rest is already validated. This is a very frustrating process. I wanted to see if anyone else has this kind of situation and is there a better way to manage this process.

Get yourself a large IP range.
Every time you add a client, add another web binding and buy a single domain SSL certificate for it.

It sounds like the stupid way around - but dealing with revalidation regularly is more painful. We’re not in exactly your position - but we are in a position where re-validating domains regularly is a frustration fact of life.