Smenkhkare and Merytaten, shown as man and wife, are pictured in the tomb of Meryre ii at Amarna, and were once shown on a relief at Memphis.
Nefertiti would hardly have married her daughter!
The "never seeing the two names together" just re-enforces the concept that they were two people, and not Nefertiti with two names
The biggest stumbling block, in my opinion, is WHY? Tell me why, in any concept, Nefertiti would have changed her name to Smenkhkara?
I thin it is possible, even likely, that she co-ruled with her husband. But I don't think she "pulled a Hapshepsut" and took the throne as a Pharaoh. I think the throne went from Akhenaten to Smenkhkara to Tutankhamen to Aye.

You are indeed correct, Osiris. And that information has to be considered alongside the fact that Smenkhkare Djeserkheperu Ankhkheperure, to give him/her the full name, sometimes had the Ankhheperure (which is the name that resembles Nefertiti's) written in the female form. and the info from Tut's chair showing that person to be i) "beloved of Waaenre"(Akhenaten) and ii)most likely co-ruling, although that again is an interpretation, albeit a reasonable one.

And then of course there is the issue of the appearance of the mummy of KV55, both skeletally and by way of the presentation of the mummy. And the move to Thebes and then back to Amarna by Smenkhkare

As I said, I do not think there is one theory which can successfully narrate all these issues, although a number of people have tried. The whole episode was evidently one of flux and factions with differing agendas.

But going back to the original post of Ankh-of-life, I would repeat that one of the problems in studying history is the application of mindsets, dynamics, or moral judgments which might seem reasonable to us but which have no bearing on the period or culture in question.

In ancient Egypt there was a very different mindset concerning gender, sexuality, promoscuity, and sexual maturity. So our classifications cannot apply.

Scribe2

PS. I mentioned Unas in the previous post, and must correct myself - it was Pepi II who was alleged to have bedded one of his generals.

To me it seems like Ahkenaton could have been transgender or something like that. I have not looked into it much though.

Modern Egypt has a different view on behaviour than us Westerners - I have been told you can see heterosexual male Egyptians walking along holding hands.

The use of the feminine form of Ankhkheperure used to be quite a stumbling block, but recently an unusual, but very logical, explanation has been bantered about.
It would seem that after his death, Smenkhkara's widow, Meryaten, disappeared from all mention in carvings and inscriptions mentioning the Royal family. A new theory has arisen. Perhaps Meryaten took the name of her dead husband, in a mark of respect for him. This would explain the feminine ending, and also the appearance of the name after his death.
This period of Egyptian history is called the "Amarna Tar Pits". It's quite understandable. It seems that the more questions that are answered, the more questions arise!