Users can access the LED on the NanoPi 2 by accessing "/sys/class/leds/led1"
Here are the commands to turn on/off the LED
echo none > /sys/class/leds/led1/trigger
echo 255 > /sys/class/leds/led1/brightness # On
echo 0 > /sys/class/leds/led1/brightness # Off

Here are the commands to set the timer
echo timer > /sys/class/leds/led1/trigger
echo 800 > /sys/class/leds/led1/delay_off # timer for off
echo 600 > /sys/class/leds/led1/delay_on # timer for on

In order to access the led1 file in Android you need permission to do it. For example you can try modifying "device/friendly-arm/nanopi2/init.nanopi2.rc" to grant permission

As for selinux issues you can try "androidboot.selinux=permissive"