I assume that you are referring to the focus of the Sun's gravitational lens when you mentioned the Solar Focus.

If so, wouldn’t the sun always be in the center of a narrow field of view and therefore require a chronograph or a nulling interferometer to allow faint object imaging. I know the Solar Focus must be way outside the orbit of Neptune but the Sun's brightness at that distance still has to be somewhat of a limiting factor. I was also wondering how stable the focal point would be if the mass distribution of the sun shifts slightly - and what effect if any does turbulence in the extreme outer solar atmosphere have on imaging.

Anyway, it's a cool idea that I hope doesn’t require a complete grasp of General Relativity to grok.