> if we send probes to ~550AU and use the Sun as a gravitational lens; we will then be able to get high-res (1km resolution?) photos/videos of nearby extrasolar planets themselves.

It doesn't scale well. The probe would be able to observe a carefully chosen extrasolar planetary system in the opposite direction in relation to the sun. If you want to observe a second system, it's necessary to launch a second probe 550 AU in another direction. You can't change targets just by rotating the probe, given its lens is the sun.