The point was that Maya implied she had seen changes to others, which were similar to a Makoto that committed suicide before. Meaning changes like Makoto's which happened due to her suicide, are not just specific to her.
It's definitely evidence that what happened to Makoto isn't actually something new in Maya's point of view. Maya didn't think much of it at all because of that. Also keep in mind that Maya doesn't actually see the other girls as real, and just assumes they'll be reset back to normal. Makoto dying, likely doesn't matter to Maya, especially considering Maya doesn't particularly seem to like her.
So, now you're saying that Makoto is an exception and death by suicide is what can't happen? I can see the logic behind it but there's nothing that actually proves it. It's just an assumption. There's also no actual evidence that Makoto doesn't actually die, before coming back. She notes it's like she hallucinated doing it when she tries, but we also know the world can alter memories and injuries. We've also seen her fall out of frame during her first suicide. It didn't seem like she came back until after she went splat.
Technically, no "people" have died permanently within Kumon-mi since Current Sensei showed up, except maybe those janitors Ayane murdered if that's meant to be taken seriously. Makoto's father was technically outside Kumon-mi and Todd is an energy draining chicken. There's nothing really similar about them beyond that something likely killed them off screen, and they aren't even considered side characters.
By obviously new, I mean in the countless resets that have occured, Makoto's father's death has never came into play before, according to Maya, and he still hasn't came back multiple resets later, which is also something odd. Meanwhile Maya has confirmed others that have died have came back, just based off how Ami has apparently butchered others, and she's noted Sensei has died more than once:
and he's obviously came back.
I've already explained how your direct evidences are flawed, at the least. I mentioned a few others in this comment though. Makoto's father wasn't even in Kumon-mi, and Todd is a chicken. There's also how neither of them are even considered side characters in this game technically, and we don't actually know how or why they died. You also seem to imply that Makoto is some special exception, yet here you are thinking that her father we've never seen, and a chicken, aren't? Doesn't make much sense.
You do realize that you kind of need Maya to be considered reliable for your "Psycho Ami is why there are only 10" theory to be plausible, right? The only evidence we have that a Psycho version of Ami actually exists is because Maya said so. There's not really evidence that Ami has actually tried to murder others before, beyond Maya's words. Still, just because she could be lying or wrong, doesn't mean she actually is.
Maya not being able to remember her death, is just an assumption of yours though. It's not "safe" at all when Makoto remembered stuff like her suicide multiple resets later. It also wouldn't explain why she could "guarantee" she'd be dead. On top of that, it assumes Ami has never truly wanted her dead, when even Sensei apparently couldn't escape her wrath, which seems unlikely. It's a possibility, but nothing about it seems "safe".
Overall: I can agree that the rules behind dying are not fully explained. There can definitely be some exceptions or conditions that we aren't even aware of.
I do doubt that Psycho Ami killing others is the reason that Sensei only had 10 initial students though. At least, based off my current knowledge.