It would be bad luck to choose a Venus-analog to map.
I might have some fundamental misunderstanding, because I don't understand how this could be.
> stepping out until the probe has gone enough distance to be sampling a separate bit of surface.
Why not have a probe already at that distance, so it's gathering something of that surface?
My assumption here (knowing very little of gravitational lensing) is that the gravitational lens still has the concept of an "image surface", where a translation in that image surfaces can be mapped to some translation in the projection of the thing being viewed. Are you saying that if I put two probes up, with some appropriate spacing between, they can't collect different stripes of the same surface, at the same time?
But if the probes are recording continuously and sending it all back, you can probably identify points that are simultaneous on two tracks, after the fact.
But that gives you just a scattering of points on that day. The next pixel over, for each probe, will be for a different planetary day. Your image, stitched together from all the lines returned by all the probes, is an image smeared over at least as many days as pixels in each line.
> The spacecraft would be taking one pixel, then awhile later another pixel, then another.
This is what each pixel in scanners CCD does. In his example, the swarm would be like the row of pixels.
> unlike your scanner bed, which collects many thousands simultaneously
The swarm would.
> watching a different bit of planet surface. Two thin line samples would not be very informative, but hundreds could be.
You would want to do this simultaneously, like in a scanner, with some distance between the sensors, so they could sample different "thin lines" of the planet, which could be stitched together to make one image, just as in a scanner. No need to wait. Regardless, a rigid physical or temporal lock isn't really required here. The concept is the same. You could arrange the swarm as a line, diagonal, grid, whatever.