In every case we have seen to the present, he is interested in some goal unrelated to any battle with the outsiders. Generally involving Holy artifacts. His move is to put a coin on someone, which he has already tried with Harry. He did it with Deidre.
Because, of course, the things we see from Nicodemus are the entirety of his plans, right?
Also, remind me what artifact we've seen that has been the most effective in battle against Outsiders, so effective that the guy wielding it didn't even realize they were supposed to be difficult to fight?
Amoracchius. A holy artifact.
And what did Mab send Harry to get, as weapons to prepare for war with the Outsiders?
A bunch of holy artifacts.
Look for the person or persons who shielded Maggie so she could have Harry.
This sentence in itself is WAG -- we don't know that
anybody "shielded" Maggie. By all appearances and the text of the book, Maggie just ran away from everyone and was away from all her prior connections when she conceived and had Harry.
The whole idea that Harry was the result of this massive conspiracy is WAG more than it is text.
Certainly there are hints that Harry's birth was special, and that
now people are very interested in Harry, but the idea that half the supernatural world played midwife to it runs contrary to nearly everything we've learned about that part of Maggie Sr.'s life.
Just to play devil's advocate here, he could have needed Harry to develop the obstreperousness that he now has--Nic has said that it is why he can trust that Harry has not been corrupted by the "Black Council."
He also apparently trusted that Deirdre wasn't corrupted.