Lets say that you get involved in the development of a large project that is already in development for a long period ( more than one year ). The projects follows some of the current design guidelines, but also has a few different, that are currently discouraged ( mostly at naming guidelines ).

Supposing that you can't/aren't allowed to change the whole project:

What should be more important, consistency, follow the existing ones and defy current guidelines or the usage of the guidelines, creating differences between modules of the same project ?

Thanks.