Lark, the extraction team, and Plutonium

Question

In MI:6 Fallout, Tom Cruise/Ethan Hunt impersonates "John Lark" at the charity event with the "White Widow".

After evading some hit men, the WW tells "Lark" that she is merely a broker, and the real price for the plutonium is for Lark to participate as one member in a gang of at least a dozen thugs in kidnapping Solomon

WW's brother already has a plan in place - divert the convoy transporting Solomon, and ambush them.

Given that they already have a plan, a sufficient number of men, the weapons, vehicles and intel needed to carry out their plan, why would they insist that Lark participate in the act, and consider that as sufficient payment for plutonium cores?

I realise this is an action movie and there is often shaky reasoning for people's actions, but this plot twist completely broke my suspension of disbelief - it makes no sense why they would want Lark (an outsider) to be in the team, especially when they've already planned it all. It makes even less sense that they'd consider that "payment" for something as valuable as plutonium cores. Can anyone offer some in-story reasoning that might back up this part of the story line?

Answer 1

Lark, in the context of this universe, is supposed to be a terrifying figure of anarchy/change (see his manifesto), who also works with Solomon Lane, who heads up the crime organization The Syndicate.

Keep in mind also, that the White Widow describes that her clients require the extraction of a political prisoner as the price for the two remaining cores. Who better to do that, then someone who has worked with Lane, John Lark? I am actually unsure if she’s aware of that connection- however “Lark” has also just saved her life at the charity auction, earning him at least one core and probably some respect.

Also, keep in mind Ethan does not follow the plan (it’s not like he throws out their original plan 100%). The plan was for “Lark” to murder all of the convoy. Obviously Ethan does not want to harm innocents, and comes up with an alternate plan that reveals he is not who he is claiming to be.