"Substance = substance"? Er...okay. 
And it's not 'having your cake and eating it too'. It's how the concept has been understood by Christians ever since we began using this terminology. Hence those who used the same terminology but with a different understanding were cast out because they were not adhering to the common faith as it had been received (e.g., Paul of Samosata, as mentioned earlier), but instead preaching their own definition, much like you seem to be trying to do.
Well there has to be
some reason I keep writing "substance/essence" and "they share one and the same divinity", and other things like that...if you'd rather use equal signs, that's fine with me.
What about it? 'Ousia' (and really any of its derivatives, either Orthodox or heterodox) is about their essence/substance, which necessarily deals with internal matters since one's
essence is internal (you can't see it, touch it, etc.), so none of this says anything about their external
anything. That's a different conversation, and not one that has any bearing on the conversation you and I have been trying to have in this thread.