Upgrade to Android > 5.0 

Hi, I see you are the only ones still doing development for OPi 3G. I wanted to ask if there is feasibility to upgrade Android version to at least 5.0. I know there are MT6572 versions of Android 5.0 and 6.0 AOSP. Would it be very complicated to make a build with android 5? The truth is that I have never worked with ROMs. 

Thank you very much.