I did some research and some tests...
I can confirm that f2fs is not stable, after mounting I had kernel oops.
My friend successfully using btrfs but on ssd drives (no nand). I think I'll try it in near future.
Also had some good news!
Tests... After system start script generate 300 files in one new directory filled with some text and then restart after short sleep and sync.
System was restarted over 50 times (over 15k files was generated).
1. After clean reboot all files where fine (no zero size files)
2. After unclean reboot (echo b >/proc/sysrq-trigger) there was different results depend on ext mount options
a. commit=600,data=writeback and journal_data_writeback enebled zero size files was ~8-10%
b. commit=5,data=ordered and journal_data_writeback disabled zero size files was ~3%
3. SOLUTION! after writing have to give echo 3 >/proc/sys/vm/drop_caches
Of course it take same time to save all data (depends on the amount of data to write) but on that system it was less then one second.
So, I my case I can use drop_caches after each write (I do not have them too many) or simply execute periodically.