With the new PlusFour, MMC has done everything right with great attention to detail. Even the choice of engine and the power-to-weight ratio. The PlusFour is a car with a character all its own. Fortunately it is not simply a choked PlusSix.
If a new 4/4 would get the same BMW 4 pot engine but with less power and the look would be the same as the PlusFour, it would not be a real 4/4 and much too heavy. The attraction of a 4/4 was not its engine weakness but its light weight.
So MMC has two different building sites to get it right, a lighter engine (preferably the 2.0 MX5) and an even slimmer dress.
Whether other than BMW engines are so easily compatible I don't think so, because the whole CX platform seems very tuned to everything from BMW, maybe it will be the BMW 3 pot, why not.
But I don't think you can make the car much narrower on CX. Even now the undercarriage of the PlusFour doesn't look as discreetly hidden as it does with the wide PlusSix. But you have to see it in reality.
I personally would not like to see such a "grown-up" 4/4 that looks like the new PlusFour (which has become wonderful in its own right).
