To see Sergio Marchionne passing through a motor show on press day - especially a North American motor show - is to see power made real. He is always at the centre of media scrum, which follows him around like a giant cloud of people.

Most the hacks involved are either Italians, fascinated by Fiat’s effective takeover of Chrysler, or Americans, wanting to know what this king from over the water is going to do to with one of their biggest car companies.

Marchionne’s audacious - and so far successful - take-over of Chrysler also means that his thoughts on the wider car industry are much in demand. Earlier this week at the Detroit show, the media were all ears when Marchionne declared Fiat-Chrysler was open to another partnership.

Some years ago, he had famously stated that a mainstream carmaker needed to sell 5-6 million vehicles per year to be able to prosper over the longer term. At Detroit he upped that estimate to as many as 8 million vehicles per year, partly due to overcapacity in the European car industry. (Marchionne added that the financial crisis in the Euro zone will hamper Fiat-Chrysler’s attempts to hit 5.7million sales in 2014).

The logical conclusion, which Marchionne admitted the following day, was that Fiat-Chrysler needs another partner, one which would help propel such a super-alliance to combined sales well north of 8 million per year.

The inevitable speculation over a suitable bride led first to struggling Vauxhall/Opel, then Volvo and then to Peugeot-Citroen, which is suffering particularly as the European new car market contracts. Frédéric Saint-Geours, the PSA brand boss, told the Financial Times that PSA is open to an alliance but that ‘the time was not yet right’.

Of course, PSA would make sense on paper because it would provide such a super-alliance with a decent foothold in China, which Fiat and Chrysler lack, while PSA is undersized in Europe and nowhere to be seen in North America. But the chances of pulling this off are, surely, minimal.

As previous collapsed mergers (Daimler-Chrysler and BMW-Rover) have shown, trying to get different companies, in different places, with different ideas to co-operate enough to use the same parts bin is probably impossible.

I can’t quite imagine the product bosses of Fiat, Chrysler, Peugeot and Citroen all being marched into a Milan meeting and being given a platform and components set and being told, VW Group-style, not to deviate from the pre-engineered parts bin when creating their next model.

And deviating from any shared component sets - think of Saab’s struggle to do its own thing under GM - would greatly undermine the point of a super-alliance. Even the new Dodge Dart is wider than the donor Alfa Romeo Giulietta, which might mean both cars cannot be built on the same US production line.

And Marchionne’s super-alliance could be dealing with three governments and three sets of unions. Imagine the uproar from the French government if Marchionne wanted to reduce capacity by closing a factory?

It’s understandable that mass-market manufacturers, who are desperately chasing the globally economies of scale enjoyed by VW and Toyota, want to try to weld together disparate, historically independent, carmakers into a single-minded whole.

But I just can’t see such a plan flying.