I've read some articles that indicate it's possible to perform a direct upgrade from Windows 2008R2 RDS to Windows 2012R2 RDS. The articles state that only the gateway and licensing server roles can be upgraded. So, they suggest that you can uninstall the other roles, upgrade the gateway and licensing server and then reinstall the remaining roles that are required. I have a small client who uses remote desktop extensively. As an accounting firm, they have multiple versions of QuickBooks and other accounting programs installed on their remote desktop server. So, it would be much more efficient and less time-consuming to upgrade the server rather than migrating and having to reinstall all of the applications. In addition, some of the QuickBooks versions are so old that we may not be able to obtain the original software and all of the updates to bring them current.
I'm particularly looking for advice, comments, thoughts from anyone who has actually attempted or done this upgrade. What if any problems were encountered? Did your apps work properly after the upgrade? Do you have any specific advice about steps to do or things to avoid? Other thoughts or recommendations are welcome, except that I don't want to hear from anyone who just wants to say "migrate don't upgrade." I already know that's the recommended path but I have valid reasons for wanting to do a direct upgrade instead in this case if possible.