Node operator-only offer as means of attracing more nodes

Why? Any restriction against the existing flow is an additional expensive spend of the developer’s time. Not needed. We can reuse the existing flow.
I’m also not sure that it would be easy to implement suggested restrictions (costs will be higher, than use the current system).

Then the invoice will be covered and the remaining amount will be used in the next invoice. So, why?

ok, four months of notification ahead is a couple of hours for some, got it.
Well, I think nobody can help with this.

here is a nuance. Consumer apps usually force you to pay for the fully allotted storage, even if you use 10% of it. This is the way, how to have a profit, of course. In the case of Storj you are paying only for what you are using (if the usage is more or equal than a minimum billing amount or if you pay with STORJ).
Do you suggest also to have a pre-paid for the full allotted storage and egress despite the actual usage? We have it too, it’s called RCS (Reserved Capacity Storage) and can be negotiated with Sales.