So you want to sell everything Goketsu gets from the pangolins in exchange for the Nara's help in negotiations? That seems excessive.
If you mean by that: "You want the Goketsu to give up everything they would have gotten to the Nara instead." then: No? Where did I say that?
If you mean by that: "You want the Goketsu and Nara to see exactly the same benefits from the deal." then: Yes, absolutely. That's the best way to incentivise Shikaku to throw his whole weight behind this, in order to maximise what we both get out of the deal. If you can have a thousand dollars for yourself, or you and one other person each get ten thousand, then you pick the latter option almost every time. It's not like the Nara are a political enemy and their gain is our loss. Quite the contrary. They're political allies, and their gain is our gain (at least so long as the power balance remains at least the same).