As you say, indirectly. Agreed that Elizabeth Line clearly *does* have connections to a monarch (let’s hope she’s still with us when it opens), and for me at least it sounds rather cringeworthy.
If we’re going for naming Overground lines at all, and I’m not convinced it’s useful nor particularly practical, it should be strictly geographical or descriptive. Why on earth would we want anything other than “North London Line” for example? And is Goblin that common outside of railway enthusiast circles?
Given how Khan seems to love promoting his own name, I presume one of them would be the “Mayor of London, Sadiq Khan, Line”?!