1. GUI admin panel to adjust all the options of the plugin
2. Compatibility with all templates, you should have excellent CSS knowledge
3. Make a special widget with full of options
4. Ability to query posts, pages, WooCommerce items, JigoShop, etc.
Note: you will just need to deal with the WordPress related things. I will help you with anything you might require related to the plugin (I am developer but not into WordPress). I will appreciate your creative ideas about this work and I want to set a long-term relationship for my future plugins.