WE do allow bounties from time to time.
Let me let you in on something. Call recording will need to be fixed in the kernel source as well. It requires a custom kernel. Some Android devices had it built in but was removed due to the variety of laws concerning it. As an example. Call recording is legal where my brother lives "if" he tells me it is happening but it is completely illegal here where I live so he cant use it at all. With call recording you have to be aware of the laws in the place you live in as well as where the other person lives. Even then if recorded without their knowledge someone could still be sued for invasion of privacy. So with all of this. Google has removed the native code for call recording.
So what you will have to do is find a device that has it built in and then compare. YOu will also need unlocked bootloader as well as a way to flash a custom kernel. Most devs have just let it go and stopped working on it.