There is a similar item already present, but the current tiers are frustrating for hobby users. I understand why you wouldn’t want open-ended access to these features as they obviously come with a cost.
I’d like to suggest that instead of locking it up entirely you limit the access for the lower tiers. So basic gets X API requests/month, and Y webhooks/month as part of the subscription. Pro gets Z webhooks/month and unlimited API, and FARM gets unlimited both. You could also rate-limit these requests to avoid lower tier users with an aggressive implementation from driving your infrastructure costs up.
If you want to get really fancy you could do something similar to what you do with storage, offering the opportunity for folks to buy blocks of additional “API” or “webhook” requests for those who really want to use the API primarily.
For truly hobby users that belong on that plan needing to spread out requersts and webhooks shouldn’t be a problem. With our largely personal use 1-2 printers running a print a few times a day at most that should work fine, but would be inconvenient for anyone trying to run a business that way.
This also gives a clearer growth path for folks. If you are starting a business but just figuring it out, the basic plan works. You get everything, just limited. You get to experiment and build a workflow. If you are successful, then you have a clear path to Pro that nets you a larger queue, more printers and no API restrictions. When you really get off the ground Farm again is just a natural expansion of your workflow to support your growing business.