I know that when changing usernames with CSC one can choose a username already on site that is inactive. Will choosing an inactive user name also work when creating a new account?

you can't have two accounts on Subeta, ever. Either the new player can get that name, or she can't: she should just try it.

The question was not whether or not I can have two accounts, but thank you for the suggestion.

Theoretically, it should work. That being said, not everything on Subeta works just because it should in theory xD

make a Ticket. They will be happy to help you.