As I still did not dare to install CoreELEC on NAN / eMMC I am using what you want. It’s easy, these are the lines of code that I included in my file /storage/.config/autostart.sh:
…
mkdir -p /tmp/internal-storage
mount -o rw /dev/data /tmp/internal-storage
mkdir -p /tmp/internal-storage/coreelec
mkdir -p /tmp/internal-storage/coreelec/timeshift
mkdir -p /tmp/internal-storage/coreelec/picons
mkdir -p /tmp/internal-storage/coreelec/picons/tvh
mkdir -p /tmp/internal-storage/coreelec/picons/vdr
mkdir -p /tmp/internal-storage/coreelec/.kodi
mkdir -p /tmp/internal-storage/coreelec/.kodi/temp
…
I use this especially to improve timeshift since I use this with several TV clients