Interesting thread....
As you've mentioned me I'll add my thoughts.
Usually what causes a 1.9 to get broken for parts is a head gasket/overheating fault. The larger engines are less prone, but still suffer the age related faults of suspension parts, rusting of sills, front wings, rear archs and wear and tear of steering wheel, seat bolsters, roof (therefore watertightness) - causing cosmetic concerns - plus age related stone chips, parking dings, kerbed wheels, dents here and there etc. Suddenly when an MOT picks up on brakes, CO2 emissions, tyres and the above a car is worth less than the repair bill (or too close to bother).
Not everyone loves the Z3 as much as people on here.
Many people want more modern cars with parking sensors, built in Sat Nav etc etc.