How to add all subscribers on sub blogs to the main blog.

there was a lot of posts on the subject around the web from the WPMU days and up to 2 years ago here and on Google on this subject of make sure that all users are added as subscribers to the main blog
I have a Multisite and would like all users that sign up on the Sub Blogs get added to the Main Site as a Subscriber User. including the Admin of the Sub Site But I will Create that user when I create the Blog.
What I plan on doing is
1. Create the main site WP Multi-User (DONE!)
2. Create the Separate Sub Sites. 5 of Them. No More will be added. Was thinking of using Blog templates or maybe Batch Create. or blog templates and Add New Users plug in Have not derided. I need to add about 100 users in all figure 20 per site
3. All sites will have the same template and same categories and Menu items. then they can add what they want to then as far as content.
4. The Users on the sub Sites need to be a Subscribing user on the main site for a Plugin I would like to implement that adds extended Profile fields so the Admins have their info, Type of Communication Equipment they own and their Amateur Radio License Class. That is if we Can get the funds to buy it or something like that thats free in another post I made but thats another Hurdle.

So to sum it up on this long Post if I have not lost you by now is How to add all subscribers on sub blogs to the main blog I just had one of my thought has nothing been written about it or asked Because W.P. Does this now? I need to check it out be back... :-<