We have a multi-tenant website where we use a wildcard SSL cert to give people a subdomain to our site. Some of our customers would like to use their own domain, but I'm concerned about how we would manage each customer's certificate as our business grows. Currently the certificate resides on the web server, which means loading all of the certs to each web server as we add them. 

I'm aware we could introduce a dedicated SSL device in front of the web servers, but are there other options to improve the management of these certificates?