The One Hoss Shay comparison would be valid if:
- Genetic engineers were madly trying to evolve a horse and still debating how many legs it should have.
- Mechanical engineers were still debating the optimal number of sides for a wheel. Somewhere between 3 and a lot.
- Structural engineers were still debating whether the frame should be made out of stone, iron, transparent aluminum or wood
- Behavior scientists were still debating what direction was best to drive the thing in and which orientation. Landscape or portrait driving mode
Obsolescence of parts is uninteresting when they have a half life significantly greater than their practical application.
Designing a One Hoss Shay in 1905 that would last a hundred years would be very useful for about 5 to 10 years. Then everybody will trade it in for a Model-T, 20 years later for a Model-A, after that figure 5 to 10 years as a function of economy.