Gabriel,
Another interesting synthesis of Mosiah Priority, Joseph’s autobiographical insertions, and the development of Rigdon’s theology can be seen in the Walter Scott innovation described by Dale Broadhurst a long time ago on this board.
As I understand and remember the argument, the baptismal formula changed around 1828, when Scott began emphasizing the sequence of 1) faith, 2) repentance, 3) baptism, 4) remission of sins, and 5) Holy Ghost, a formulation Rigdon appears to have adopted.
What is interesting is that the Book of Mormon seems to capture the transformation of this theological view. The original, older pattern can be seen in Benjamin, Mosiah, and Alma, but the newer formula emerges in Mormon and Moroni before solidifying in 2 Nephi 31, which suggests a compositional timeline much longer than that generally expressed.
Under Mosiah Priority, what reads as Nephi’s foundational doctrine in what would be chronological order is probably the final, accepted view as seen in dictation order.
For example:
Mosiah 4/5: Baptism isn’t mentioned as necessary for remission or rebirth.
Alma 36: No baptism between repentance and rebirth.
3 Nephi 7: baptism is a witness of something that has already happened. So it’s 1) repentance, 2) remission, and 3 baptism.
3 Nephi 11–12: only a few chapters later, big change. It’s now 1) faith/repentance, 2) baptism, and 3) fire/Holy Ghost and remission.
Moroni 8: Mormon’s letter is very close to Scott’s formula of 1) faith, 2) repentance, 3) baptism, 4) remission, and 5) Holy Ghost.
2 Nephi 31: finally, 1) repentance, 2) baptism by water, 3) remission by fire and by the Holy Ghost, 4) enduring to the end.