I am in favor of anything what takes the One ring away from King Dain's hand!
Time inconsistency definitely isn't obstacle, especially in Edain. We can find it in every faction.
Much more problematic is when someone is in game out of character and generally it seems strange or doesn't fit. One thing is how the concept is playable, second thing is how the concept feels.
For instance I really like Thranduil's shield bubble, but doesn't feel right for him. For Celeborn or Glorfindel? Maybe. For battle mage like Gandalf? He already has shield bubble. But definitely not for the king of the Wood elves, where magic isn't present like in Lothlorien or Imladris, thanks to rings of power.
The same case is for me old Dain using the One ring.
All right then, your name will be in the green list, Tiberius
I agree with you and also I add this consideration; As I just said multiple times: here, in this specific case, Durin VII is not just a revival character coming from the past, but an actual reincarnation of his forefather. We absolutely cannot say anything similar for other character like Eorl the young or Gil Gilad for example. The lore speak clearly about a return of Durin, and since Durin VII will be the last, it is probably the most similar reincarnation of Durin first. That's why I actually don't understand why we should compare him to other ancient character. It's a different case here.
Also, we know that he ruled and lived during the fourth age, but we are not absolutely sure about his birthday. So, rather than inconsistency, I would speak about different lore interpretation
. Furthermore, being him an heir of Durin he has probably very long lifespan such that we cannot exclude he lived let's say from a bit before the end of the third age (see our timeline in the concept) to the end of fourth age. The lore says that he will guide his folk until the end of dwarven age.
By the way, the team will probably discuss this matter (I mean Dain ring system in general) before the 4.5, since I don't think they are going the let the Durin revolution incomplete. So, let's see