Keep in mind, the current course of the world if nothing changes is that Mari sets off the EM contingencies and many ninja across the EN learn of it. From there, once someone reinvents it, nothing stops the inevitable chain of logic that other agents will also reinvent it and that it's impossible to defend against the nuke either directly or though diplomacy, and in fact their village is simply doomed unless they kill the entire rest of the world first. That is to say, in the world Orochimaru has created civilization has months left to live, maybe half a year, before one way or another the village system ceases to exist. Given ninja mentalities, this is essentially impossible to avert once the word starts spreading.
Which isn't to say, overall, that we couldn't do what you suggest. But we'd be on a time limit before "and then the apocalypse happened", and as players we would know this even if the character didn't. To me, that kind of saps most of the interest out of the idea. There's no shot at making a meaningful difference, no way to beat the odds and try to make something of ourselves, make a better world for the future. It'd kind of just be us idly playing around with a disposable nobody of a character until the setting unceremoniously throws them in the trash.
So for me, no, it's Hazou ride or die. At this point, given how all the dominoes fell, he's still the only character that can meaningfully be the protagonist of this story.
I feel like following up on this a little more. In what world does Orochimaru prevent the incoming apocalypse?
I don't off the top of my head know if Mari's had the time to set up the deadman's switch independent of her. That is to say, it's possible that Orochimaru just needs to kill her, but it's also possible that he'd need to either interrogate her and hunt down her contingencies or convince her to disarm them herself. Both scenarios, however, require Orochimaru to take action against Mari before she reaches Leaf, at the very minimum.
How likely is that minimum? We know that Orochimaru doesn't think that any deadman's switches Hazou has are going to be too problematic for him. Moreover, however, even the ones that
are troublesome are most likely in his head to take the form of "Hazou designed a special rune" rather than "Mari does something". It's always possible, of course, that Mari is the one instructed to activate Hazou's deadman rune, but even that scenario has its limitations: Hazou has only been to so many places during his journey, and infused runes can only exist where he's been. There can't be a deadman's rune in Leaf threatening his Basement, for instance, since Hazou could not have pulled off that kind of infiltration job.
So he's unlikely to see the deadman's switch as a true threat to himself. Even if we prepared a special rune, we can't have done so in a position that actually threatens his interests meaningfully. And what else could we have done? Poisoned his reputation further? As if. Overall, I simply do not see a route in which Orochimaru concludes Mari must be dealt with immediately for the sake of preventing the activation of a dead man's switch.
Therefore, if Orochimaru is to avert the apocalypse, he must take action against Mari for some other reason. He has little reason to act against Leaf's manpower as things stand, but it is perhaps plausible that he wants to kill them to remove runecrafting OPSEC breaches. This is not a job that can be fully completed, however: not only was the existence of runecrafting made public long ago, Naruto and Tsunade both know that it has been reinvented in truth. He can achieve a degree of relative secrecy, but it's not like he can fully put the genie back in the bottle. Nonetheless, among all the people who know of runecrafting Team Uplift
does present the greatest continual risk to it leaking, given that they may be more zealous than Leaf's upper brass and more inclined to spite Orochimaru for killing Hazou. While it's by no means certain that they would leak the reinvention of runecrafting to Orochimaru's enemies, they might, so Orochimaru has a motive.
...a weak motive, all told, compared to what it would take to kill Mari here. Mari is certainly not going to follow Orochimaru into the woods where she can be easily disposed of, and in all likelihood she's not going to stray far enough from Tsunade that she could be attacked without bringing approximately half of Leaf's firepower down on Orochimaru. That's the kicker, I think, that seals Orochimaru's fate. When he's already pursuing such an important objective as "relocate the rift to a safe location", attracting too much heat right now is unwise. Especially since he can just pick them off later, when less is at risk.
So in my opinion the odds of Orochimaru attacking Mari before she returns to Leaf are miniscule at best. And with that, his fate is sealed. Once Mari gets back to civilization she'll start to spread the information, and once the information is out not even Orochimaru will be able to stop the world from learning about it. Therefore, with extremely high confidence, the world's gonna end yo.