An interesting detail from this article is that Akhmetshin claims he was asked to attend the meeting with her by Veselnitskaia only that morning, and had to show up in jeans and a t-shirt.
Certainly implies that:
1) he and Veselnitskaia had an established working relationship,
2) Veselnitskaia had an agenda wherein Akhmetshin’s presence served some sort of purpose for her.
Unless she needed him as a translator, why would Akhmetshin be useful to N.V. if her real purpose was to pass along documents about the Clintons (especially documents that would need further verification?). He would be a superfluous witness to that (unless him talking about it later WAS the plan). On the other hand, he ,like N.V., was a paid advocate for Russian opponents of the Magnitski Act; N.V. hijacked the meeting to make her case on that issue, so possibly she wanted him there to assist in that.
Options:
1) N.V. and her bosses used hustler Rob Goldstone to get a meeting using the false bait of Clinton-compromising material, while actually intending to lobby for repeal of the Magnitski Act. Possibly they thought this was a way to open a channel of communications with the Trump administration in case Trump was elected.
2) The above, but it was all a ruse to create the appearance of Russian election interference, either for the Russian government (or business interests); for Democrats/Hillary supporters; or two mints in one.
3) N.V. was trying to trade anti-Clinton efforts for help repealing the Magnitski Act, but Trump Jr. either didn’t get it, or deliberately acted that way.
The Russian ambassador supposedly brought up relaxing sanctions in calls with Flynn. Huge oligarch money tied to the Kremlin must be at stake (I suspect US interests related to Obama, Clinton, and the Democrats benefit from keeping them in place). The whole “Russian collusion” thing seems to lead back to efforts attack the sanctions.
The Akhmetshin angle has only served to complicate the matter to the point where the descriptions of the meeting aren’t even coherent anymore. N.V. and Akhmetshin have described the meeting so differently that it doesn’t even sound like they were both there at all.