Or: before SaaS we used to have the model of one-time purchase + annual maintenance fee (which was a small percentage of purchase, like 5-10%). The benefits of the "maintenance fee" to be defined by you. But it used to include updates of software and in enterprise context often support.
I think you need to have a demo use case in your app so people can better understand what this is about.
I tried to make an invoice document type. So far I got simple header data and line items and I created a method to add up line items to a total. It would be nice if methods could be triggered to run automatically. I can place buttons to run methods, but can I run a method at document update or field update?
Also I to speed up creation of methods you should have simple aggregation function like summing all items of a list (given a field name to sum over).
It has happened several times to me that I have not seen a customer's email because it was marked as spam and likewise customers have not seen my email as it was sorted in their spam folder. This is a breakdown of communication that is far worse than spam.
A classic use case that is more likely to be flagged as spam is when a customer submits a request via a web form or on social media and you try to follow up by email. From the receiving email server point of view this is a cold email and in danger of being flagged as spam.