The question that can be asked is “why be limited to a region”? When the Ğ1 was launched the question was asked to make a single currency or full of small currencies, one by region. One currency per region is to limit its economic impact. And people do not want to waste time with something that has a weak impact. It would seem rather better to make a change for Brazil, so that it shines more.
Already replied here: Ğ1 paired on Ethereum, with value and tradeable with Bitcoin and other cryptocurrencies - #33 by DaniellMesquita
But these parameters are not immutable and can very well change over time. In any case, Duniter at the moment could not technically support a million members who would make daily transactions.
It is good.
So, if a state/province is with a little more than 3 million members, these values can be updated through a HF.
Regarding the millions of transactions, sharding could be considered.
It seems to me that the parameters of the Ğ1 could very well be enough at first to launch your currency. All that remains is to make the genesis block.
What are the maximum member and geographical distance G1 haves?