If you had to build out a team of PMMs from scratch, how would you organize your team and which roles would own what?

Sounds like your business is growing - how exciting! It's hard to answer this question without knowing how your business is structured but I'm happy to share common structures for 10 pmms. Structurally, a people manager or team lead should have at least 3-4 people; this is typically a good "pod" size and enables your people manager/team leads to scale. So with 10 pmms, you could have 1 Director with 2 people managers with 3-4 under them. When b2b businesses are growing, typically the focus for pmms are on product development and launch so typically I've seen pmms aligned to products/parts of the product portfolio. But this is very different for b2c where typically I've seen pmms aligned to audience segments (e.g. smb, comm, upper comm).