If by "another candidate" you mean "other than the Celts," you still have to make that story work. I still see no plausible amount of time and no mechanism to turn Israelites into Celts in about 110 years. Why the change of language? Why the adoption of a new paganism, not even the old Canaanite paganism?
Isn't it less of a strain on the brain that the Celts were just another tribe like so many others that was out of sight of civilization until they wandered into contact? That any group of people exported from Israel wasn't all that large and probably was absorbed somewhere? Why do you have to force the two to match? It doesn't work.
It really is not even necessary to make the story work. But even so, we have centuries to work with in order to get them to Europe.
When it all boils down to the residue, whether you accept that the Northern Kingdom tribes made it to Europe or not, whether they changed their language or not (You can find the list of roots words in "Missing Links Discovered in Assyrian Tablets" by E Raymond Capt, pp 187-198), or whether their culture changed or not, the fact of the Hosea 1:10, 11 prophecy (also found in Genesis and Ezekiel) remains.
If God's Word can be taken there will be a major population right now of the descendents of the Northern Kingdom. Whom would they be, unless the Celtic related peoples?
Further, is there anything basically wrong with the European types peoples being the descendents, which would justify the frequently emotional reaction of people, out here at least, to that idea? You know what I mean. You can almost hear the echo in the outraged posts: Oh God! No! Not them! Anybody but them!
Why the adoption of a new paganism, not even the old Canaanite paganism? What was "new" about it? The children of Israel were already half way there. The reason Israel fell was the adherence to the Ba'al worship of Jeroboam son of Nebat. Read Kings II for a stirringly repetitive and boring recount. My take is that the "new" paganism of the Celts was reasonably coherent with that of Israel.
Isn't it less of a strain on the brain that the Celts were just another tribe like so many others that was out of sight of civilization until they wandered into contact? So you have a "Hollywood fight" theory. In a Hollywood movie when the good guy is surrounded by bad guys in a fight, all but one never engage the good guy at once, they wait till one goes down and then the next one steps up. So you think that the Celts, whose descendants rule the world now just sat around and did nothing hidden away somewhere while the Israelites, Assyrians, and Babylonians all got off the stage. The same peoples that ruled the world in 1000 BC rule the world now.