I prefer personaly use an ext4 system and extend the eMMC (or uSD) with an additional partition where I copy the system root (and mount as / for extroot)...
Then fstab (block-mount ipk) take care of any crash and check fs with the option :
config 'global'
...
option check_fs '1'
...
config 'mount'
option target '/'
option uuid 'replace with correct uuid found it with blkid command'
option enabled '1'
option enabled_fsck '1'
It is a 24/24 7/7 365/365 solution which is crashless !
No problem with sysupgrade, but you'll need to replace then the added partition content with the sysupgraded rootfs content...
I have done some "ugly" scripts to take care of this type of installation; available here :
They also take care of adding ipk at upgrade and firstboot...
Mostly working on espressobin board arm64 custom firmware but may be enhanced and fixed to be more stable and use also on any board like the RPi !
The poweroff, unplug, crash of filesystem is easily fixed with this method / scripts...
An automated reboot may happen after a filesystem fix...