There are 2 places which can benefit from enhanced processing of wildcard SSL certs. (having just spent an hour on this due to a cert renewal ... its something I know could be improved...)
During the install, Certificates are asked for twice. IF a wildcard cert is presented in the services dialogues, then the panel question could be preceded with a 'reuse services wildcard cert?" question and save the time re-entering something that is already known.
In the Panel itself, give the ability to enter a wildcard cert for the domain, and when adding SSL for any sub-domains, allow the selection of the wildcard - or the existing functionality. Updating the single instance should (obviously) update all the subdomans that are using it. The time savings and convenience of setting up/maintaining single entries would be a considerable improvement.
A tool to "spray" a new cert out to existing i-mscp installed servers would also be a huge benefit to those with multiple servers.
While not many users are apt to purchase wildcard certs, I know people with multiple servers, and those with multiple subdomains, would find it very useful.
(no rush for me though - I'm good for another year )