Add all users to main site as subscribers on Multsite network

Hi,

By default when you have both BuddyPress and Multisite enabled, users are added as Subscribers to the main blog (e.g., at mydomain.com). I'd like to add all users to the main site by default in my multisite network without using buddypress. I know this question has been asked a thousand times. Just want to make sure I'm approaching this according to best practices.

Thanks!