So I'm revisiting this idea again. I'm wondering if this would really be that hard. After some time looking at the code tonight here is the idea I'm working with right now.
I'm thinking of splitting the USERS table into two tables, one with a new prefix that would be the Universal login table for instance ubbtlogin_USERS, and ubbtcc_USERS. The ubbtcc table would contain membership level and session info that would be specific for each site. I would also have to do the same for the USER_PROFILE table, splitting up the data that is unique for each installation and that would be universal.
Obviously this would require a lot of recoding, but it's only changing the queries.... unless I'm overlooking something. There are 179 instances of {$config['TABLE_PREFIX']}USERS.
