Do you think that Wyman Manderly is sincere in claiming that the old customs officers were still loyal to King’s Landing or is he taking the chaos and inexperience of a new administration to consolidate his power in White Harbour with more loyal/less scrupulous appointees?

Both.

Here’s the thing about our good friend Wyman Manderly: he believes in doing well by doing good and vice-versa. He’s always going to be there for the Starks, and he’d never be so crude to demand to be compensated first…he’s not a Frey after all. Instead, he steps forward as the good vassal in times of need, and then he comes forward with all kinds of helpful suggestions about how he can be even more helpful if he was given all kinds of new offices. And it’s understood that, just as it would be crude to demand payment in advance, it would be rude to deny such a loyal vassal such a minor favor…

But here’s the thing – he’s not lying about any of it, because he doesn’t have to. Of course the royal customs officers who were in place before the War of Five Kings aren’t going to support a rebellion against the Iron Throne, so they need to be replaced. And I’m sure the people who replaced them were loyal to Robb Stark, because Wyman Manderly would have made sure of it. Likewise, establishing a mint or a royal navy are absolutely in Robb Stark’s best interests – but they’re also going to rebound to Wyman Manderly’s benefit by boosting White Harbor’s economy and military power. 

Where things get trickier is the Hornwood Question and what happens when Wyman starts conflating what’s good for House Manderly and what’s good for the North. On the one hand, Wyman was perfectly happy to play the normal Northern political game when it came to the Hornwood lands. But when Ramsay broke the rules and it didn’t look like Rodrik was going to do anything, Wyman didn’t hesitate to occupy the Hornwood lands “for their own protection.” And that’s the kind of thing that can be politically destabilizing, and you get the sense that, as with Garth Greybeard, the Manderlys were not entirely innocent when it came to their feud with the Peakes. 

But…and this is important, they’re still mostly constructive, and as long as their liege lord maintains a firm hand, giving them enough of a return on their good work without giving away the shop, and making sure that the rewards get spread around liberally and the Manderlys are made to play nicely with the others so that jealousy doesn’t give way to feud, they’re a credit to their kingdom.