First, like most Lotus road cars of that era, most of the alignment is not adjustable. Chapman didn't trust his customers not to mess it up.
"the rear control arms are light little wispy things, reminiscent of hollow bones in birds’ wings"
BS. In the direction that they are designed to take load, they are more than adequate. I had the stock rear lower control arms on my Special with wide (205s, really wide for a Europa), modern (at the time, which was the 90s) sticky tires. The original rear control arms held up fine (as did the "weak" u-joints (the upper link in the rear suspension on a Europa).
However, those control arms don't hold up well when loaded on other directions, like from the side. From the photos, it looks like someone jacked up the car under a control arm, which is not advised.
"The rear toe is adjustable via a Byzantine arrangement involving spacers (washers, really) on the bolt connecting the rear trailing arm and the subframe."
Byzantine? There is a bolt that goes straight through a rubber bushing, a shim pack (to set the toe, if you used washers, I hope at least that they were the correct thickness), the end of the trailing arm, and finally a washer and nut.