What the fuck are you even
You're arguing in bad faith. Why the hell are you assuming that Madoka would die in a month? She'd never even have to fight in her life. She'd never need to hunt for Seeds. She'd have no trouble maintaining her Gem, because of a big supply of Clear Seeds and at least two veterans watching after her health at all times.
After all the problems we've had with Sayaka, you think
Madoka, of all people, would be willing to sit tin the back with her thumb up her butt?
There's some pretty serious implications of power incontinence that could kill her in one shot. Madoka is firmly established as an active martyr who refuses not to be as "helpful" as she can be, even if that means her own detriment, and even if we keep her stocked up with Clear Seeds and under heavy guard to keep her from running off and going full Kamikaze on some random witch somewhere, we'd still need to make sure she's somehow happy with the situation or Homura is going to turn into Murderface. Not to mention the moral implications of making someone wish away their soul and then locking them in a tower like Rapunzel. Sure we could let her have all sort of luxuries, but she'd basically be living in super-Oriko conditions for literally the rest of her life. Which could well be infinite.
Er, no. She has no such established habit. She's done that...what? Once? Twice, maybe? And that was because she's used all of her power at once to kill WPN. She's not guaranteed to Witch out immediately out of fucking nothing. That would be nonsensical.
Besides, with no Witches, Madoka can't Witchout. So it's not even a hypothetical risk. Not that we'd ever even need to let things get that far, but still.
Even so, a gem filling with grief will be lethal, either through the gem breaking or from suicide if we somehow prevent that.
And, uh, yes, it's quite established that Madoka commonly burns all her power on her first shot. Yes it's usually on WPN, but there's some seriously strong implications that she's got some sort of power incontinence. Even if not, we still have the problems outlined above where we have to keep someone who literally could become a god, and may as well be one for all the magic power she has, locked up in a room somewhere. Who probably won't appreciate it, I might add.
I, for one, don't see us being on the receiving end of whatever Uber-arrow she shot Walmart Nugget with. For some reason, I don't expect us to survive.
How is it a gamble? Madoka got exactly what she wished for. When Mami warned her what the consequences would be, she said that she knew and was okay with that.
That she didn't think of "create a god who would do the job for me" and instead went with "do the job myself" is the problem.
Wishes don't come with hidden monkey's paws. Kyouko's Wish gave her exactly what she wanted; where things went wrong is that she told her father about it all and he couldn't handle the realization. Considering that he was willing to let his children starve to stubbornly continue trying to be a street-side preacher that no one listened to, I'd say we weren't dealing with a very rational man in the first place. Sayaka's Wish also gave her what she wished for. That Sayaka also wanted Kyousuke to return her affections but didn't Wish for it is the problem. Arguably the only Wish that doesn't grant exactly what is desired is Homura's, which makes her case all the more odd, because it stops just short of giving her what she wants...maybe. It could be that, if Homura hadn't decided to discard all timelines in which Madoka contracts, she could have eventually succeeded. After all, she did nearly succeed in the third(?) timeline, where all she needed was one more grief seed.
Just because the monkey-paws are built into the universe and not the magic, doesn't mean that there aren't monkey-paws. The Madokaverse seems to have karmic balance built into it - pretty much everything good that happens in that show is balanced by something bad. Even Madoka's canon wish is balanced by her disappearing and Homura being forced to live on as the only person who remembers her; basically to create heaven, Homura has to live in hell.
I really don't want to find out what Firn thinks about this topic, but I'll be willing to bet that from a game design perspective, it'll have to be balanced by something equally awful. I really don't want to find out what happens when both God out-of-universe and Goddess-in-universe are pissed at us, one for wrecking his plot with stupid bullshit and one for screwing her over like Flava Flav in a Tiki-torch shop.
Again, it doesn't fix everything for us. It only fixes one thing: Witches. Everything else--improving the lives of magical girls everywhere, keeping our friends safe and happy, creating some kind of global organization for magical girls--would still need to be done, and they would still be challenging.
Oh, so it's okay because we only cheated on the hardest question on the test? Without witches, keeping our friends safe and happy would be literally the same job, since our major threats would be the pissed pinkette in the tower and Homura's slow descent into waking PTSD nightmares, Sayaka's moral quandry of being a hypocrite or letting Madoka out to die, Mami questioning if
she's safe from
us, because now we're locking up our friends like some sort of faux-Stalin, and all the other issues therein. And establishing a nation, yeah, that's definitely hard, but it also doesn't really have the same level of failure state that witches do, because if we fuck up all we've failed to do is create something. We can't actually lose.
So no, it's not okay. It'll be a shitstorm even if we do do it, and it would be utterly uprooting the very basis of the quest in favor of another one. It's like sitting down to a D&D game with a shadowrun character sheet and then trying to argue that it's not cheating because it just changes all the problems: THESE ARE THE PROBLEMS WE WANT. WE WANT TO SOLVE THEM FAIRLY.
Your solution is not fun. In the end, and I hope this doesn't enter Sabrina's thoughts because it would be horribly sociopathic for her, but for us it's relevant, fun is all that matters. Literally nothing else matters except whether we're having fun here, and your solution is simply unfun. It's not a entertaining way of solving the challenge we're given, it's not fair and it's not clever.