Yes, this. If they actually wanted to retcon the dagger into the One Ring, then fine — but they’d need to do a lot more work to make it plausible. Along the same lines, if the dagger is such a corrupting influence (presumably once’s you’ve held it and ordered a Dark One around with it), then how come Gideon just hands it back, no questions asked? Wouldn’t the logical reaction be “ooh, I got me a Dark One, lets go take out the Black Fairy now”? And why would Rumple give it out to Bae in the first place if it has such a horrible effect (unless, of course, he doesn’t know)? They do have material to work with, both in-universe and in terms of folkloric tropes if they wanted to suggest that this sort of power is both literally and figuratively corrupting. It certainly would explain why no one tried to order the Dark One out of commission, and locked the dagger away — which, of course, has a lot of precedents in all sorts of fairy tales. They could have done such an interesting speculation on why the proverbial genie always ends up imprisoned in some lamp somewhere: that eventually someone somewhere grows a brain and realizes that this kind of power is bad news for everyone. But my point is that if we all have to collectively do this much work to make this whole thing make any sense at all, they’re doing it wrong.
It is odd that Gideon was not seemingly affected by holding the dagger. But perhaps holding the dagger doesn’t mean you want to be the DO or control the DO. Maybe it just means you want to continue lusting for dark magic. So for him, it’s killing the Savior. Once he took it from Rumple, his willingness to still do that and go to the blue fairy to get her blood increased. And there have been others who controlled the dagger or became the DO who all of a sudden, turned into a crazy person. Hook, Cora (although she was a psycho and sort of always wanted more power), Emma a little, Rumple obviously, Arthur, and now Baelfire. And as you say, they have material to work with here. But they probably need to flesh out the control the dagger and the darkness can have on someone more consistently, if that is the way they are going with this.
But then again Gideon seems to be the exception to the rule in some situations. Given that he was raised by the black fairy and memory potions apparently don’t work on him, that the black fairy tried to make him go dark for 28 years and failed, being the product of true love and the son of the dark one (Bae was conceived when Rumple was human and he hasn’t magical so it wouldn’t apply to him the same way). Maybe he’s just somehow inmune to being seduced by the darkness?…. just a few thoughts….