Taking on from here: https://central.owncloud.org/t/fork-nextcloud-appstore/1436 what would you like to see? what to avoid? Please share your thoughts to make this great!
I think NC did a lot of things pretty good already, because they could start from scratch.
First thing is to extract all information from the info.xml.
This ensures that you have one consistend source also within the xC App-App itself.
I published the Audio Player as a test there also and compared to copy/pasting all this info into the OC-Store: this is the feature I would go for first