At the end of the day, as an enterprise, you have a target financial outcome: some combination of target income and profit. If a cohort of customer is willing to spend assuming a one time payment model, and you can successfully manage expectations for those customers (while minimizing the burden of doing so), it is reasonable imho. The pitfalls are customer unhappiness and the economics performing suboptimal compared to your forecasts (they become a support or engineering burden because they feel entitled to it outside of the previously agreed upon scope).

Maybe don’t offer it publicly, but test it with a a customer or two who really wants it to see what the experiment shows. Wishing you a successful experiment.