Publish Remoteapp from UNC Path

Chrisvanaz , hopefully I'm able to help you out. Are you trying to publish the executable from UNC path? For example, an executable from an application server? I have a similar setup for my customers, the only difference here is that we've managed to run the application from UNC path based on a shortcut.
1.Create a folder (example c:\program files\shortcutapps\ )on your WVD session host, or put this folder and files in the image
2.) create a shortcut, target path pointing to your application/executable 
3.) Put the shortcut (.lnk file) in the c:\program files\shortcutapps folder.
4.) Create an application group, add the application, select file path instead of start menu, application file path c:\program files\shortcutapps\app.lnk
I have tested it many times, it works. However, running the client native from the WVD session host vm gives way better performance. Keep that in mind!

Good luck!