How to allow guest bloggers in subsite

I have a multisite with paid subsite users. Some of them want to allow guest bloggers on their site. I know there are plugins for this that allow front end submissions, but what is the easy way without using plugins built into multisites. I think the settings are different than a single install which allows you to set up "anyone can register" and then assign a default role such as an "author." Is there some equivalent setting for multisite? I looked at one subsite under Appearance > General, but did not see the same settings.

Thanks, Joe.