Steve,
You are right and I suspect this is why the Morgan family was wise to accept the Invest industrial opportunity. What Investindustrial hopes to gain is an interesting one: investing in a mature "combustion engine" business doesn't make sense, so it must be something to do with the skillset and operational scale (currently a weakness for all the reasons you suggest). However, I can see the logic of offering a coachbuilding service to customers as electric cars replace outlawed combustion engines and individuality retains a premium...in many ways this is what MMC actually does now.
