Hello,
I have seen a lot of potential in selling items with bundle. there is one marketplace that allow authors to create bundle of their own products and sell them as all in one package.
So if you join to his/her membership you can pay once and access to their files for certain month including updates and fixes.
After certain period which defined by author, if the buyer wants to receive new updates, author can charge him/her with small amount like (10 - 15)$ per month in order to access new updates and fixes that released newly by author.
I think this is a great idea, and you can make it happen, if you need further information about this method I can name the marketplace then you can go and research more about the whole idea.
Thanks