I've made something[1] that used "jq for everything" in the past.
RequestHub was initially a way to connect webhooks from one service to API calls to another services, using jq scripting for all the customization.
Later I realized it could be used for processing anything (even text!), not only webhooks, but it was too late. Maybe someday I'll do a Yahoo Pipes revival that will just use jq for scripting inside the boxes.
I think Zapier and the likes fill this need pretty well. I wonder if there's still a niche for more lower-level hosted service for plumbing webhooks though. It might be a rather small niche unless you figure out a way to offer better value than those guys.
One thing that definitely makes it hard is the chicken&egg situation. I can't imagine many people paying for a service (or even using it for free), unless it has a solid reputation and is highly available. Otherwise, they'll either host something on their own, or use one of the bigger players.
RequestHub was initially a way to connect webhooks from one service to API calls to another services, using jq scripting for all the customization.
Later I realized it could be used for processing anything (even text!), not only webhooks, but it was too late. Maybe someday I'll do a Yahoo Pipes revival that will just use jq for scripting inside the boxes.
[1]: http://archive.is/nGyH3, https://github.com/fiatjaf/requesthub.xyz