i confess i struggled to get the value proposition at first. i tend to look for as simple as possible positioning. people can get behind "no code", people can get behind Jamstack/"empowering developers", but pitching the messy middle is very tricky in my mind.
i think where i was swayed is less in the custom components part, but more the integrations with airtable/other APIs. you might have a decent shot of doing that better than wordpress and webflow can (although both are formidable already). as a marketer with some dev time i might find that very useful.
with the custom components piece, i'd lean into more of a marketplace approach so that people can reuse components made by others/pick them off the shelf, and people who maintain components might even be able to make money from the weweb users who are using them!
as for embedding React in Vue - what are the constraints to simply mounting the React component on a DOM node rendered by Vue? are you solving for SSR or something? its not clear from your description what exactly you are struggling with.