Canoe the North recently put up a YouTube video of a very similar trip. It was from Stanton Bay to Poohbah and back. He did it the hard way. It does include going upstream on the Maligne. From Nym you could join this route on the first day. I think it would probably be easier to head west out of Batchewuang to McAlpine, Kesakokwog, Quetico, Jean and then Sturgeon.
Stanton Bay to Poohbah