Forza Horizon World Cup

I don’t get the actual point of this. There are supposed to be competing countries yet possibly 90% of the British cars, for instance, have German or generic rally engine swaps. Why do I have to use a Merc V8 or an Audi V10 if I want a competitive car in S1 or s2?
Why can I only get sub 900hp from a 5 litre Jaguar engine? Or why can I only get 500 something hp from a cossie engine? Why do I have to engine swap to a V6 or V8 to get any real performance? That has got to be a joke.
For all cars to be fully competitive the engine swaps should be the same from every model. instead of whoever is in charge restricting each models performance and cherry picking the models they want to be popular.
Some cars have 3 or 4 times the engine swap choices, so how is that competitive?