I'm not currently subscribed to Hubs, but I've read that for the moment there's only support for one hub per account.
I would be of the view that it's not enough. Some people may need or want to have multiple hubs, configured differently and with their own assets. Perhaps they are configuring hubs for different uses, or clients, or even purposes. The only way to do that would either be to create new Mozilla accounts for each Hub, or asking somebody else to work on it, or have that someone give them access to the Dashboard through the account.
Maybe there could possibly be the option of creating more than one hub. Maximum 2 or 3, to begin with, each of course independent in having its own subscription. This could also serve to explore whether there's the need to support a large or small number of hubs for admins. If there's a lot of people who max out their number of instances and ask for more, then that limit could be extended further up. Otherwise, this number could be fine for those who may need the flexibility of managing more than one hub.