Help getting Arabic on Android
I'm Persian and also have Nexus-S. You can upgrade your ROM to Ice Cream Sandwich (Android 4).

This version of android has Arabic in it's localization and has all you want. If your provider support oem upgrade you can simply upgrade it by phone OR you can flash the latest Cyanogenmod ROM to your phone and have fun with your mobile.

You can always download latest Cyanogenmod Naghtly from HERE