I don’t think that systemd has a whole lot of sleep-management architecture that does what you want? What it does have is the ability to do “suspend-then-hibernate”, which would suspend for some set time, wake up, and flip over to hibernating. I’ve set that up on Debian (not too hard), Ubuntu (pure hell), haven’t tried on SteamOS.
What you want is technically possible without changing the hardware or firmware, but I think it would take an unreasonable amount of systemd coding.
https://wiki.archlinux.org/title/Power_management/Suspend_and_hibernate#Changing_suspend_method
I think the xray is from ifixit? I nudged trimming it until the port and volume up button lined up just so.