Plan: fairy godmothers. Isha being back on the scene will open up some opportunity's, including a possible way to get another god. The long imprisoned goddess of life being free and getting hitched is the kind of pivotal moment where gods can be born, if you clever about it.
Requirements: Isha hooking up, Yennead* would work but most any other god would do, we're also going to need the Immaculate Order up and running.
Risk: hoo boy, if you think mortal births are risky. The number of ways that a divine birth can go bad start at the kid eating the mom and go from there.
General overview: So typically, a god gestating takes a long ass time, but like all things in the warp with enough power, knowledge, and narrative you can bend that. Now the narrative we have to play with here is Isha at long last being free, ushering in a new era of hope and growth and striking a grave blow against rot and stagnation, some pretty fantastic narrative fodder and relevant to huge swaths of the galaxy. Knowledge wise, well we have the black library, if there is a way it's in there somewhere. Power wise, is where things get interesting. See, when your trying to do something specific the kind of power matters, if your trying to do something boring i'd be no good, but even a small good of boring crap would be great**. Now you can again, bend that at a premium in power, but gods are tied to there themes. But what if you had a lot of gods? The story of a child being born and receiving divine gifts is an old one, and if things work out with Zahaks mob we're going to have a whole pile of gods with useful domain kicking around. The idea Zahak came up with, with no ulterior motive i'm sure,*** was to essentially use the members of her mob who proved themselves trustworthy to broker power. We'd give the gods with useful portfolios a big dollop of power, an exchange they'd use most of it to make a blessing for the kid. This could in theory let us do a whole lot to shape and enhance the god. Course there is a hard limit of what could be achieved, the story of the golden child who will fix everything forever tends to end poorly. That would still leave us a whole lot of wiggle room though, being able to build a god from a wide array of parts could be big.****
* work really well. tying life and death together adds another load of narrative weight.
** and you wonder why you can't get a secretary.
*** you can't prove anything!
**** they would also be someone unattached around for one Big E shows up. Divine marriage alliances across racial lines would be useful.