You have not needed an IP address per certificate for years now. It indeed used to be true you needed an IP per certificate a decade ago.
About catch-all certificates, most of the public CAs discourage their use, and often will refuse to issue them.
As far as I know ngINX supports SNI (Server Name Indication), and as such, as long ngINX is compiled with SNI support (by default nowadays), it is a matter of configuring several (SSL) vhosts.
The point of SNI is also not having to create a multi-host cert. You create a different certificate for each vhost. So vhost www.example1.com is pointing to the certificate of www.example1.com and the vhost of www.example2.com is pointing to a different certificate that only contains www.example2.com.
From How To Set Up Multiple SSL Certificates on One IP with Nginx on Ubuntu 12.04
Although hosting several sites on a single virtual private server is
not a challenge with the use of virtual hosts, providing separate SSL
certificates for each site traditionally required separate IP
addresses. The process has recently been simplified through the use of
Server Name Indication (SNI), which sends a site visitor the
certificate that matches the requested server name.