Bill Gates is all for multiple chips, especially if he can collect for a Windows license for each one. And the IC manufacturers would love him for it -- think of all the extra hardware to support Windows.
Speaking of fancy computing aboard vehicles, does anyone know if the remote diagnostis and control I saw illustrated for a large diesel truck is standard on all or most of them these days or is it an option?
Well, we don't know what exactly you saw, do we?
But yes, all but the most trivial ECUs in cars and trucks are diagnosable to at least some extent, these days. Automobile companies usually have a blanket requirement stating something like "every ECU has to diagnose all its inputs and outputs, and report its internal status in sufficient detail to know if these match each other".
Electronics repairs of current cars consist of little more than:
acquire tester for this make&model find diagnostic test socket plug in tester ask for error read-out wait a bit peruse output (optionally have customer OK the costs) exchange culprit part lather, rinse, repeat from step 4
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