I recently submitted an app that was rejected because it did not use app blocks for displaying information on the storefront. I am not sure this is possible for the app. Documentation from Shopify is lacking, and support said they will only answer technical questions posted in the forums here.
The other two options are to 1) store settings data as metafields, which would not work in this case due to the amount of data required and Shopify limiting private metafields to 10, or 2) retrieve settings externally from a database. This would add latency, introduce possible security issues, and overall be a less performant (and more expensive) method.