I read it and I don't see there anything that clearly convinces me that this language is distinct enough.
For example, it's not quite clear to me whether the different letters are actually used by the general public, by newspapers, and by writers, and whether they are used when teaching literacy.
It often happens that language academies standardize something, and the new standard has some fans, but it is not actually used by the general public. If, for example, I had a reliable source that says that more than half a million people in Montenegro want to read and write with Ś and Ź and with the other special Montenegrin spelling rules, and the admins on the sr and sh Wikipedias are preventing them from doing this, then I'd say that something should be done about it. I can think of two examples of what *could* be done:
1. Convince the admins of sr or sh Wikipedia to be more accepting of different spelling standards, as it is already done in English, Portuguese, Alemannic, Catalan, and other languages. I'm not familiar with a process to enforce this, and I'm just fantasizing, but it's an imaginable option. The fact that bs and hr Wikipedias already exist doesn't mean that more proliferation is needed.
There can be more things that could be done. But it would really depend on the need.
Do Montenegrin schoolchildren learn literacy differently? Do Montenegrin people use Ś and Ź in WhatsApp messages?
Do they use search engines like Google, Bing, and Yandex with Ś and Ź, and with a significantly different spelling? If they do, do the search engines fail to find relevant Wikipedia articles?
I'm trying to be practical and think about the general public of speakers. If the current setup of Wikipedia projects leaves out more than half a million Montenegrins, this needs to be fixed. If it only leaves out several dozens of people who want to promote a new spelling standard, even if this standard has its own ISO code, than I'm inclined not to change anything.