Andrew Connell walks through the Office 365 Patterns & Practices Scenario adding App Script Parts into pages within an App for SharePoint. This code can be found on GitHub here https://github.com/OfficeDev/PnP/tree/master/Samples/Core.AppScriptPart
Good examples of the pattern usage is for example Yammer embedding mechanism or how interactive maps are integrated to the sites using Bing or Google
This provides more seamless and dynamic integration option than using app part which are IFrames. This also means that this is suitable option for example for responsive user interface design. So this could be definitely something to evaluate also from app model perspective. What if we would actually just simply deploy redefined script web parts to the SharePoint sites which would have the reference and needed html for provider hosted app reference. This would give the end users opportunity to add additional functionalities to the sites as needed using simply normal SharePoint user experience.
In production we could be running these scripts easily from Windows Azure or from any other centralized location where they can be referenced from the SharePoint pages. This also gives us easy way to update the script, since it's not stored in the actual SharePoint page, it's rather loaded completely from the provider hosted environment.