Do you have any plans to offer a solo professional type plan? ~$350/year and up is quite a lot more than I can justify for what I would use this for. Something like Automattic's Premium plan ($8/month) for a managed blog with a subscription system like this would be an easy sell for me.

I understand if that's a hard no. You seem to be aiming at people who are or plan to be big time enough to hire people to help. Getting people in who might head that way so they have an easy upgrade path might be good though. If I were the kind of person Patreon's top plan aims at, any Ghost plan would be an easy sell, but even thinking about that is a long way off for me.