Pal, as it's Christmas time I am awarding you the point, as the MG is the odd one out, but not for the reason that you've given. I will explain...
All the above cars have a link with De Tomaso, but the MG SV X-Power is the odd one out, because it is the only one of the six cars NOT have been sold as a specific De Tomaso model variant with De Tomaso branding visible on the car.
The De Tomaso versions of the Bertone Innocenti, Dodge Omni 024 and Daihatsu Charade (Mark I and II for the Japanese market) are well known. Less familar though are the De Tomaso-branded versions of the Mark I Ford Cortina and Simca 1000 that were both sold in Spain in the 1960s. After the Festive break I will scan in some photos of the De Tomaso Cortina and Simca.
Thanks for everyone's inspired contributions to this puzzle, and more 'odd one out' puzzles to come in the New Year. Until then, Happy Holidays to all.