Like @Sabru said, you can not treat a faction's allies as enemies, while playing with that faction's ID.
However, you can play long enough to become official, and so have the right to roleplay changes in their diplomacy with sense.
So, instead of just using a faction's ID because it 'looks' similar to your original faction's idea, I'd suggest RPing as though you are a different 'wing' of that faction. You're not in control of the whole faction as of yet, and have to still play by their set up rules and commands. Even if you do not like it, until the right time.
When you have gained the officialdom, more choices become available to you, as far as I know.