So I was thinking about alt-wind!Mathilde since someone brought that up, specifically the only other type of wizard we were given at character Creation:
Amethyst. So lets run this through
Intrigue Advisor
STIRLAND
Faith: Morr, since kid!Mathilde Kidthilde if you will (

) took up Ranald worship since she would get favor for things she would already do I think this one would go for the death god
Petty and Lesser Spells: Sound; Magic Weapon; Aetheryc Armor, solid picks and no reason to change them
Relatively Simple Spell: Death's Messenger (temporary bonus to intimidation) so she would have some kind of non-combat option.
Apparition: Bleak Swarm, I went with this over Rotwyrm just because being a swarm of invisible observers had potential for later
Sleeper Agent: I'm going to leave the
Lahmians here even though it would have been harder for them to snare a death mage the way they did Regimand, no reason to unduly change the world
First thing that comes to mind is no Shadow steed so strategic mobility isn't in the cards, but lets say this Mathilde too has a good roll on her first use of Death's Messanger. What would be the scariest thing to a bunch of vampire thralls if not a vampire? So instead of just looking like herself but more scary Mathilde would gain the seeming of unlife. After maybe potentially almost getting staked by Van Hall she gets the idea of how to use this for more than intimidation since she is still a clever journeymanling with a high intrigue score, pretend to be a vampire to catch out their patsies in the stirland league, heck maybe she even manages to catch her predecessor.
The second point of divergence that now comes into focus is how does Morr differ from Ranald? Well he is not a god of luck but of death and dreams. So I'd say the favor of Morr would come in the form of insights in dreams about whatever project she focuses on. As she aquires more spell abilities like
Final Words and
Knocks of the Departed would go some way to getting her more information on vital projects even as the fact that Morr is a more acceptable god would mean that she would have an easier time using his Church for official help. Who knows maybe this Mathilde learns swording from the Black Guard? Since she is an Amethyst wizard I imagine she would get more use out of those barrow blades maybe even pick up one of those to fight with.
Lastly lets circle back around to that apparition. These things are meant to feast on rot so this Mathilde would have an aversion to dead bodies so maybe instead of optics she gets some anatomy books. What counts as flesh? Lets say she prepares a special box with some ripe cuts of meat and offal inside them as soon as the swarm manifests flash fry the whole thing. So Mathilde does so and with a little help from Morr it works. Dice still lands on 50. That it turns out that was troll meat with a bit of the magic still in it so when in contact with the already magical and partially Ghyan aligned warp beasty the flesh heals as it burns, a gout of perpetual controlled warp-fire.
Not going to go any further than this since realistically Mathilde would not act anything like the same in pivotal battles and other moments since she does not have the same skill-set or experiences.