Alternatively for PMMM.
The Plot: Homura is an amnesiac and traumatized magical girl who lost her glasses, Madoka finds her and becomes friends with her, Madoka's family adopts Homura. However, at the same time this is happening, other Magical girls are getting REAL close to Madoka, one of them even turned out to be her best friend! But the group MUST return Homura's memories with her (and with them her coping skills) or else she'll create a Walpurgisnacht with her frequent PTSD episodes.
The 'Mascot': Kyubey is creating magical girls to fight entropy, buuut how the decay is fought is very different from canon. Kyubey's more honest and upfront with the girls, there are thousands of Incubators on Earth. Kyubey's actually the 'Sponsor' for Mami's House. Magical girls in this universe are categorized into Lone MGs or House MGs, a House Magical Girl is a Magical girl who's part of a Magical Girl House. If a Magical Girl House is sponsored by an Incubator, it means that one particular Incubator makes equipment and even recruits Magical Girls for that specific group! Kyubey is sponsoring Mami.
The System: Trag-I mean, Magical Girl's soul gems no longer corrupt on their own, they do the opposite, they get brighter and more powerful as time goes on until they reach maximum capacity. Meaning they don't need to hunt witches or else they become witches themselves because it literally can't happen unless a Magical girl is inherently evil! Overexert yourself and you die if you're not a psychopath. Why would you hunt the Witches? Well...
The Enemies: "If Magical Girls are born from wishes, then Witches are creatures born from curses. Magical Girls bring hope to the world, Witches bring despair, and since they're invisible to humans, they're that much more insidious. Anxiety and mistrust, rage and hatred, they sow the seeds of disaster all over the world!"
Well, Kyubey in this is a bit more honest, replace world with universe and you'll have what he says in my revision. Witches are very different in nature from their canon counterparts! Witches are born from the rampant negative emotions of a large amount of people at the same time and the desires of the evil, or monstrous people committing evil acts.
This anime is still dark, since many Witches are either presented as victims, IE: bad things happening to them, in which case they're mercy killed. Or perpetrators, IE: murderers, torturers, thieves, betrayers, and rapists (yes, some witches will try to rape people to death, but those are rare in Japan), so yeah, PMMM is still dark.
However, the Witches source of magic isn't actually powered by their own souls. In our world witchcraft/LEGIT black magic is practised by sacrificing humans, often babies, these witches gain power and do magic by luring innocent people to their deaths with witch kisses, AND EATING AWAY AT THE FABRIC OF THE UNIVERSE. So yeah, Witches are termites who upped their game, the problem is made all the more dire by the fact that they can't be combatted with ordinary weapons. You can't throw an army at half of them and do any damage.
The Characters: Mami is...mostly the same, less lonely 'cause she has a couple other MGs by her side.
Sayaka is the same, just less angst and more survivability.
Homura...amnesiac and has literally forgotten both the cause of her trauma and how to get over it.
Kyoko is the most different here, she's somewhat the same but more ruthless and more caring for the common people. Instead of "Familiar Farming" Sayaka has a massive beef with her due to her methods, which involve stalking and murdering the evil people who the vast majority of the more dangerous witches are born from, preventing many of those witches from being born. Kyoko supports her arguments by stating that Witches can be born from the same person more than once, and the fact that her father was tortured and killed before her eyes....the pain and horror of his murder spawned a Witch.
Madoka: About the same.