I know tmagp is suppose to be able to be enjoyed by new fans with no prior knowledge. So Martin and Jon being around is like. Maybe a passing Easter egg thing later.
But Jonah Magnus being in it, when the fucking Magnus Institute being burned down is one of the main hooks, shouldn’t be that far fetched. Chill. Even with the fandom going rabid a Jonah Magnus reveal will still shock and awe a newcomer.
Even if he’s not alive or not a voice. Just learning about the dude, Fears or no Fears, should be eye opening to the story