I am not sure if that right is required after installation, however you must build the ePO database through the ePO installer.
About the only option I can think of therefore is that you install using a different Sql server (Use the bundled MSDE version locally if needs be) just to get past that phase.
After that move the DB to your Sql cluster and point ePO at it through the https://servername:port/core/config page on the ePO server.
No promises this will be a success though, given the rights applied.
n.b. 'default' collation is a requirement. If your Sql cluster is otherwise configured you may still have issues.
How was your experience? Did you get ePO DB on the created instance?