The only real problem that I have,
@Azel, with your plan is that you have Viserys coming around and saying, "I do not wish to break Ironborn culture", and yet he is putting an end to as many forms of slavery as can be found reasonable (which essentially means
all forms within his own lands, and the trafficking of them that passes through them). That puts an end to thralldom.
He also hates banditry, and tolerates piracy mostly because it has an added benefit of stifling the slave trade. The raiding of
only slavers barely pays for the upkeep of his fleet as it stands. His real profits come from
trading. And he knows this.
So he wants to put an end to piracy, thus taking away their Iron Price. He wants to put an end to slavery, putting an end to thralldom in the cradle (for however long Balon managed to revive the practice, and to whatever limited extent before Lord Harlaw took over regency).
He wants to increase the fertility and industries of the Iron Islands, making them profitable, and in all likelihood focus their sailing efforts on protecting trade and hunting other pirates, and yes, maybe even similar marine actions. While loot is inevitable, in order to enact this policy change, it will take more centralized authority than every ship captain being able to sail at their own leisure and decide what operations they'd wish to be part of. Optionally, you could become a patron of Asha's newly expanded Iron Fleet and give her more negotiating leverage against the individual captains by encouraging her to own all of her own House's ships outright, rather than pay upkeep for her captains out of the loot they gain. Because
loot will be more irregular, while steady salary will not.
What we want to do to them is basically strangling their culture and the replacing it with a changeling. Superficially similar, but different enough as to not be two and the same.
It just seems kind of disingenuous to try for diplomacy and to convince her we're the right horse to support, when just about the only thing of worth she, as an Ironborn, perceives her people have left is their culture.