M:M relationship schema, how to get around it?

Hi Community,

I am wondering if there are recommendations to get around M:M relationship targeting? Below is a diagram of our identity structure. At the web login (email level), this is where our onsite targeting happens. However, under each Web login, there can be multiple billing accounts, but each billing account can be associated with multiple web logins (e.g wife & husband have their own unique logins). 

We want to target at each unique Web login level, however, with private graph enabled in our Merge Policy, AEP automatically consolidates all the Web logins & Accounts into a Single Profile because there linked identities. We need the private graph because we also need to use the profile attributes from the billing account profile fragments.

Is there a way to isolate each UUID, and the associated billing accounts into unique profiles?

I've been told B2C is the solution we need, but that's not in our roadmap to migrate over yet :(. 

Thanks!