Alfa Romeo is going to launch a new, lightweight Spider in 2015. And it’s almost unthinkable that it will be anything other than excellent. How? Because underneath, it will be the next-generation Mazda MX-5. But it will have Alfa’s own body styling and engines.

The two companies announced the co-operation this morning. They even announced that they expect to get the Alfa into production in 2015, in Mazda’s own factory.

The all-new MX-5 itself will come sooner than that, because Mazda has already been developing it for some time. Alfa’s designers have to design a new body to fit the platform from a standing start.

By 2015 Alfa will also have launched its new high-tech 1.8-litre engine, which will also power the mid-engined 4C. It’s good for 230bhp in basic form, but Fiat has said it can go up to 300bhp in future. To be honest though, 300bhp will overwhelm the MX-5 brakes and suspension, so it’s unlikely in this car

Suddenly then, Alfa has a credible range of rear-drive sports cars. This little roadster as the accessible choice - remember the MX-5 (pictured above) is the world’s best-selling roadster. Then the 4C as the icon.

Gallery: the Alfa Romeo 4C at the Geneva motor show

Finally, Alfa has been planning, ever since Fiat Auto and Chrysler got together, to do a rear-drive Spider based on the Chrysler rear-drive platform. But that’s bigger and heavier, and has already been delayed. This new little Mazda-based confection (which will go on sale in America as well as Europe) might kick it into the long grass altogether.

Anyway, a new little Alfa Spider? We’re salivating already.

But there’s more. The last line of today’s joint Fiat-Mazda statement reads: “Fiat and Mazda have also agreed to discuss further opportunities for co-operation in Europe.”

Now, Fiat-Chrysler’s boss Sergio Marchionne has already said he’d like to find another partner. And Mazda has been losing money for four years. It looks increasingly isolated and undersized now that its ties with Ford have been cut. And at the moment Fiat is also losing money on its European operations too.

The current Mazda2 was co-developed with the Fiesta, and the current Fiat Punto was co-developed with the Corsa. In both those cases, the new-generation cars don’t have an obvious platform partner. And sharing a platform lowers costs by sharing development and tooling costs, and by bulk-buying components.

How about the next Mazda2 and Punto getting together? The conversations between the two sides have only just begun, and they’re not confirming anything. But neither are they denying it.