Buddypress only directed to subdomain within a multisite?

Hello,

I want the users to be connect throughout the network/multisite, but this is only accessible on the frontend NOT backend i.e no users allowed backend only frontend. I don't want users to keep re-registering every time on the multisite.

Is it possible to direct every buddypress member to subdomain when they go to their buddpress profile i.e instead of domain.com/buddypress direct to buddypress.domain.com.

Current theme doesn't look good with buddypress so if I used a different theme on a subdomain that would be better.

Thank You+ Points will be rewarded.