But do you need 300 pops to benefit from the edge model? Or would 10 pops in your primary territory be enough.
Cavaet for high scale sites and game servers. Maybe for image heavy sites too (but self hosting then adding a CDN seems like a low lock in and low cost option)
If your usecase doesn't require redundancy or high-availability, why would you be using something like Cloudflare to start with?
Having a local backup user is a viable backup path then. If you wire up pam enough you can even use MFA for local login.
More seriously, I think there's a distinction between "edge-style" and actual edge that's important here. Most of the services I've been involved in wouldn't benefit from any kind of edge placement: that's not the lowest hanging fruit for performance improvements. But that doesn't mean that the "workers" model wouldn't fit, and indeed I suspect that using a workers model would help folk architect their stuff in a form that is not only more performant, but also more amenable to edge placement.
I don't think that the number of PoPs is the key factor. The key factor is being able to route requests based on a edge-friendly criteria (latency, geographical proximity, etc) and automatically deploy changes in a way that the system ensures consistency.
This sort of projects do not and cannot address those concerns.
Targeting the SDK and interface is a good hackathon exercise, but unless you want to put together a toy runtime to do some local testing, this sort of project completely misses the whole reason why this sort of technology is used.