Hello,
I completely understand your requirements. I have develop custom plugin based on requirement many times. Also worked on customization of Plugin like Woocommerce, Buddypress and many more.
I can work with page builder and able to develop drag and drop functionality in the plugin.
Also I am ready to show you demo of working of drag and drop feature.
Further i am very much interested in your project and i will complete this project in stipulated time.
Please feel free to chat with me here.
Thanks,
Priyanka