Since your service has great network speeds and are dependable, it would be nice to have a distro/application image for the official FreePBX distro as an option for new droplets. It is a great system for SIP based VOIP that offers both ease of use and security if desired. You can hook it up to abilities to call external normal phones and everything. However it is not easy to initially get set up.
Making this official distro available and updated will mean people can easily choose you over other providers due to you making this official ready to go distro image available.