There are plenty of supposed Steam Deck killers available in the portable gaming space, from the Asus ROG Ally to the Lenovo Legion Go and all the Ayaneo and ONEXPLAYER devices in between. But none of them have managed to outright slay the dragon that is the mighty Steam Deck yet.
They already took so much care to handle the suspend feature (they even support save syncing mid-game!). Solving the point you mentioned is the one thing that, in my view, would make it perfect.
The thing is that it’s technically possible to handle this use case… they could have programmed it so it goes into hibernation after X hours of being asleep (which could have been done by setting a wake up timer before the sleep state, the Linux kernel already allows it).
I wish some of the unofficial extensions implemented something like this, but I bet it’s not so simple to hook into the pre-sleeping / post-sleeping codepath without messing up too much with the system… plus the risk of potentially causing the device to enter some inescapable loop.