Bodhicitta and the path of knives? Is cutting off the "path of knives" (i.e. avoiding rebirth into lower realms) not the ultimate?

I mean, obviously it's unlikely any Buddhist seeker would affirm that. But, given life on earth can be improved for humans, is it not very like the ultimate, to never again accrue evil karma and rebirth into hell or animal or ghost realms?

Also, do any of the schools which say some sentient beings lack a seed for buddhahood, self enlightenment, and arhatship, claim that those sentient beings can forever avoid rebirth into the evil destinies? 
And in what way can they work for bodhicitta?
The aim should not to be to avoid reincarnation in 'lower' realms, but to alleviate suffering for all sentient beings. Please do keep that in mind. Focusing on reincarnation encourages selfish thinking.