This is a rather open-ended question. Can someone explain to me all the possible connections there are between Mehrunes Dagon and Akatosh, as well as the connections between Mehrunes Dagon and Alduin (I have no problem with those categories overlapping)? I know there are some, spanning from the Aldudagga text (not only the LDK's fight with Alduin, but his tenuous connection with Magnus and the position of Magnus as the Witness in the Akatosh/Lorkhan enantiomorph) to the end of Oblivion, but I don't know them all, nor can I keep them straight. I'm looking for a reason for Mehrunes Dagon to train and release mortal Dragonborn prisoners who had been trapped in his realm in order to thwart the return of Alduin, despite the fact that doing so directly helps Imperial Akatosh due to the identity of the Dragonborn I have in mind (one of Uriel Septim's sons; see the thread I just started in the Morrowind General Discussion Forum regarding the presence of doppelgangers in Uriel Septim's household) and the secret maintenance of the Covenant thought broken by the death of Martin Septim. I have this vague notion that there are enough connections between Mehrunes, Akatosh, Alduin, possibly Magnus, and various Daedric Princes that I can finangle a possibly-over-complicated motive for Dagon's willingness to interfere with Alduin's plans despite the benefit to other parties. My fanfic plot requires Dagon to be willing to put another Septim on the throne, regardless of the cost to his chance at making himself king of leapers again.
If you think I'd just be better off finding a different Daedric Prince to be my Dragonborn's "patron," please tell me that, as well. I can just as easily pretend that Mehrunes Dagon's defeat at the end of the Oblivion Crisis allowed another Prince to sneak a few notes to his pocket-realm prisoner while Mehrunes himself was weak and distracted--well, unless there are metaphysical reasons why that wouldn't work, either, in which case please tell me that, too.