I meant that I removed the stock keyboard (LatinIME), deleted using SystemAppRemover of AICP Extras and installed a different one (I used Fleksy). That gave the phone enough system space to install both GApps and Arise Sound System.
Steps:
1. Install a different Keyboard app. (Google Keyboard, Fleksy, Swype, etc.)
2. Remove the system app LatinIME /system/app/LatinIME (can use System App Remover AICP Extras or manually with root access using File Manager)
3. Install GApps and ARISE Sound System. (I use OpenGapps and AROMA installer of ARISE Sound System).
---------- Post added at 06:49 AM ---------- Previous post was at 05:56 AM ----------
I can install pico GApps or ARISE Sound System individually but not both because it would require more system space and the stock keyboard is the easier one for me to replace to be able to free up the needed space. You can remove other system apps to free up the needed space if you don't want to replace the stock keyboard.