That exact system is already in place, you earn points from survival/battle/breeding and spend them in future runs to get bonuses. There's more to flesh out on it, of course, but the core is in the game now. It's a good start, but I do still understand the desire for people to have a save system, just from the "it feels bad/makes the game pointless to lose my team when I quit" perspective.
On the other hand, that's pretty clearly something the dev wants to happen so the constant asking for it isn't going to go anywhere. I'd imagine the idea is that the limited-and-random-stone system combined with the constant restarting is intended to make you react to what the game gives and build around that instead of building some theoretical 'perfect team' and doing that every run.
There's downsides to this, obviously, as people are quite validly pointing out. I'd imagine a lot of the complaints would be silenced if there was an "ironman" save system that only had a single slot and deleted the save on loading it so no savescumming is possible (more of a pause/resume run), but to some extent it makes sense to me to focus on content first before working on that- save stuff is notoriously annoyingly break-y across frequent updates, so any save stuff done now would likely end up being invalidated fairly frequently anyways.
