Using one SSRS server to organize (folders / subfolders) reports hosted on several other SSRS servers

I have several SSRS servers (for SCOM, System Center, etc..) -- referred to as SourceSSRS servers -- in different versions (2008R2, 2012, 2014), each having its own SSRS reports organized in folders and subfolders.
The users wish to go to a single SSRS server -- referred to as CentralSSRS for the lack of a better word -- and find the reports they are interested in that are hosted on the SourceSSRS servers.
On CentralSSRS, reports are grouped according to users’ needs. For instance a folder may contain reports coming from different SourcesSSRS Servers.
I thought about downloading reports from the SourcesSSRS servers and then uploading them to CentralSSRS, but this proved not to be easy (several reports from 2012, and 2014 failed to upload to 2016, and many failed to open in vStudio 2015). Even if this issue is resolved, a report on CentralSSRS will have to be refreshed (download & upload) each time the source report is modified, such as a result of an upgrade.
There is also the option of having, on CentralSSRS, reports that contain a simple list of URLs to source reports. But creating these URL-reports (one for each folder and subfolder on CentralSSRS) can be pain. In addition, they have to be updated each time a source report is added or deleted or when the grouping changes (such as when moving a report from one folder to another).
These 2 options are far from ideal. There must be a better / easier way.