I found a way to use third-party controls from optional packages

[BlameTwo]

I just changed the way the controls are loaded in the UI, first of all, you're right, if you use this. InitializeComponent(); causes xaml parsing to fail, but I changed the method of loading resources in Application.LoadComponent, and I changed the enumeration of the third parameter to ComponentResourceLocation.Nested so that it doesn't have a reason why third-party controls failed to load, but Hot Reload is still not available.