I don't know much of the technical details of how a branch is created, but some experience from my mission may be helpful as you consider whether or not to proceed. One of my areas (in Arizona) had three stakes, and each stake had a Spanish branch. At a certain point two of the branches were consolidated into one bigger branch (spanning two stakes) and the third branch was dissolved completely.
I don't know if the direction came from area seventies, or just a decision by the stake presidencies, but what they told us was that foreign-language branches exist for the language, not the culture. Almost all of the members in the branch that was dissolved, and a few of the members in the branch that was combined, were able to get along well enough in English. It was difficult for many of the members, but they were told to go back and support the English wards in their areas.
What I took from that experience is that language branches are to meet the needs of those who would not be able to have their spiritual needs met in English. They are not for commonality of culture. Again, I don't know if this is general church policy, or local decision, but it made sense to me.
Samuel Bradshaw • If you desire to serve God, you are called to the work.