That was really well put. Add to that the worry about Granger's potential enemies and detractors, as well as those of his father, who will look askance at any reward being given to someone they perceive to be an enemy. Jealousy and backbiting were very much a part of the Royal Navy of the time, especially since commands, promotions, and assignments were largely meted out to those who had influence.
George has a basic modesty that adds to his charm, and makes things like a peerage, which some would assume, seem totally surprising to him. I think much of that stems from the fact that he doesn't really have to ask for anything (as opposed to Nelson, who was quite vocal about what he thought were reasonable rewards), other people fight those battles for him. He's the golden boy who gets to remain oblivious about backroom machinations, because the earl or Caroline or his other friends are back there pulling levers for him.
If Granger were made a peer, he could become Lord Granger, or Lord Somethingelse (picking a geographic title). He wouldn't be Lord George Granger. Having his first name in the mix would only have been used if he was the younger son of a marquess or a duke. Lord Henry Paulet, for example, a Royal Navy officer at the time, was the younger son of a marquess, and was titled that way. We'll see if Fletcher turns out to be good or evil.
I'm actually stretching history here with the iron water tanks. They wouldn't become standard Admiralty issue until the early 1810s, but they were used in experimental applications as early as 1796.
Giving Granger a peerage wouldn't mean that the King was granting him land, although in the past that had been done. The first Duke of Marlborough, for example, was given an expansive grant of land and a sizeable award of cash from Parliament to build Blenheim Palace. It's more likely that the peerage would be granted based on the land and wealth that Granger already possesses.