According to some opinions (see Shulchan Aruch OC 146:2 and 685:7; and others), one is obligated to hear parashat Zachor read among a minyan, but one can (and must) read it without a minyan if there is no minyan. (I am not interested in discussing the nature of this obligation, or whether the minyan is obligatory or preferable.)
I am interested in the question of gathering a minyan in order to have a second reading of Zachor (for those who may have missed the first one). Assume that at least 10 men have gathered (who have not already heard Zachor), and there is thus reason to take out the Torah and read it (see for example Mishnah Berurah 685:17).
Although I have seen the gathering of at least 10 men for such a reading, I have never observed other minyan-related activities (such as brachot or kaddish). Perhaps "reading in a minyan" mentioned in the halachic codes is simply code for "reading in the usual ritual spot"?
So, reading Zachor for/in the presence of such a crowd: (a) Is there any fulfillment of the minyan requirement/preference mentioned above, or is this simply a collection of individuals hearing Zachor? (b) If yes for (a), is there a requirement to say a bracha before and after on the reading, or kaddish after? (c) If yes for (a) (and no for (b)), is there anything needed to establish the minyan, or is the presence (and presumed attention) of the minyan sufficient?
Some of my thoughts not already mentioned: for (a), perhaps there is no room for "public ritual readings" that come with the other practices outside the established times; but perhaps "reading in a minyan" is simply among 10. For (b), we normally say brachot on public Torah readings, but this is outside the established time. We normally allow our morning Torah brachot to cover non-ritual Torah learning. Anecdotally, I've never seen a second reading done with a bracha. But perhaps since this is a reading of something required, we would say the brachot regardless. I saw in Minchat Yitzhak 9:68, that R. Weiss was asked about saying brachot at readings specifically for women, and he said not to because they may not be obligated, implying that for men one would say brachot. The answers to this related question might imply that brachot should (or must) be said amongst a minyan, but that may only be talking about delayed "full Torah readings", not just reading "one aliyah-worth". For (c), I recall something (somewhere) about the public recitation of Bar'chu or Kaddish at the beginning of public prayer establishing a minyan, so here too something might be required.