Use French when no translation
I disagree with your project of changing the actual default language when no proper Breton version is available.
Yes, that was clear. I'm trying to see if there is some principle we can agree on, so that we can star from there to build an agreement. Not answering my questions does not help.
I've been trying to answer your question(s) the best I could for about a week now, with no success I confess, it seems your mind is already made from the start. You want to change our fallback language (because we're French and French people speak French), something nobody is asking for on our wiki (because precisely we're trying desesperately to survive with a litte bit less French around in our life and building an enciclopedy in our language is one of the answers for that). Therefore, I don't see what kind of agreement could possibly be on the table there, or it is English, or it is French.