Could you use the JSR package registry instead of setting up a new one?

I agree! It seems the author is already making thoughtful decisions on what to implement and what to drop. You kinda have to when it's a project of this scope.

Implementing, running, maintaining, scaling a module registry is probably not worth the time. Unless there's a clear technical requirement from the runtime. I would think there isn't since npm protocol compatibility is a stated goal/feature.

+1 to this.