I kind of jumped in on this conversation at the last second so if this is
covers old material im sorry. A lectotype, in my view (i could be wrong),
stends from the timer where a species was thought to have an essence and this
lectotype describes or represents a "perfect" specimen. Any variation from
this perfect specimen would just be considered a mutant of this perfect
species idea. In a species in which there is great variation I can imagine a
case where they describe what a perfect specimen should be and even help the
description with a drawing. So if this line of thought is right you do not
need an actual specimen to serve as a lectotype.
Emilio Jose