Heliostats on the roof beamed the sunlight down to the Solar enlargers in the darkroom. The mirror in the heliostat was driven by a clockwork motor to keep the mirror at the correct angle as the sun arced across the sky. The enlargers stayed stationary.

There is the old concept of 'chemical focus' - it dates to the days of wet plate photography. Collodion is sensitive to UV and so after attaining 'visual focus' the camera was racked in a bit. TTBOMK, the amount of adjustment is always a constant distance and doesn't change with magnification.

I think the idea of resurrecting a true 'Solar' enlarger is appealing.

http://notesonphotographs.org/index....Solar_Enlarger

Google heliostat for more

You can make a heliostat from the drive and mount for a small astronomical telescope.