CoreBOSBB

another idea would be to create a perspective that installs the cbrelations module and adds the hook directly wherever it is needed. that way anyone could transform their coreBOS installing it

To be honest I think this should be the 'default' behaviour and the 'one account per contact' setup should be available as legacy. Backwards compatibility should not stand in the way of progress. Especially since you're moving to a B2C and B2B separation, I think a loosely based, flexible and versatile contact <-> account relation model is more appropriate. We should create some kind of user interface to select contacts from accounts and vice versa (like step 1: select contact and step 2: select relation with account) to make the connection process sort-of-single-step process like it is now.