Currently, they only way to provision a workflow to site collections is to use the exported wsp-files from SharePoint designer. This however requires custom scripting to be enabled.

For on prem you may use a farm solution but this is not applicable to SPO.

If this was handled by the content type hub there would be no dependencies on the old feature framework.

http://blogs.msdn.com/b/chaks/archive/2012/05/05/workflows-and-content-type-hubs-whats-the-story.aspx