Is this a question regarding updating your deposit method in the Seller Central or your Amazon Payments account?

Here you can review the instructions for updating your deposit method within the Seller Central:

https://sellercentral.amazon.co.uk/gp/help/help.html/?itemID=G851&ref_=ag_G851_h_r0_cont_sgsearch

And here are the ones related to Amazon Payments:

https://pay.amazon.co.uk/help/201212230

What you propose sounds like fraudulent activity to me.
You want to add a 3rd party recipient for the cash from the sales made on your account?
Why not simply transfer the money to your own bank and make a bank transfer to the 3rd party?
What you describe seems like money laundering

That doesn’t sound like a good idea at all.

I have a UK and German bank Account and when sales in the EU marketplaces picked up and I needed access to more euros decided I wanted to add my euro account (which from buying stock was running low on cash) i had to go through a whole bunch of verification that the account added matched my details.

So if you add a third party bank acccount you may not be able to pass amazon verification checks.