It would be a big help if we had the ability to associate a Flow with a SharePoint content type. The capability I am describing would be similar to what is available with a reusable 2010 style workflow created with SharePoint Designer.
The capability should include:
The ability to automatically use the Flow anywhere the content type is used within a site collection or site collections
Attach the Flow to the content type definition
The ability to optionally use the Flow anywhere the content type is used