This mod will add init.d support to any rom even stock roms without editing the ramdisk. Instead it uses the post_boot.sh file that is in most if not all roms. It should work on most devices, if it does not work on yours please look in /system/etc and post the name of the file that contains "post_boot.sh".
This mod has been tested on the OneX and OneS.
To use just flash in recovery and add your favorite scripts to init.d.
To add this method to your rom simply edit the post_boot.sh file and add this line at the bottom:
All files in init.d will be executed at boot just like regular init.d. You can also manually add the line and make it whatever directory you want.
I have attached a test file to flash to see if init.d is working.
Flash Init_D_Test.zip in recovery
Reboot and navigate to /data and look for a file called Test.log if it's there Congats init.d works.