Doesn't this fight against the previous Large Mailbox articles? The idea of creating a database/organization relationship was because of Single Instance Storage. Now that SIS is gone I think it's actually bad to put everyone on the same team on the same database. You want to spread your users out. That way if a database does go down, at least everyone else on the team still gets their mail. Plus people change teams, or certain teams might jump in email usage, causing the database to bloat unproportionatly.
Now I can see goodness if the New-Mailbox cmdelt had a -DatabaseAvailabilityGroup parameter, so the admin could point the new mailbox to a target Dag and Exchange can workout which database in the Dag to use. But that should be the extent of the scoping.