Adding a whole preference panel for an app_template

I am the main developer of the BlenderFDS addon that is used to describe geometries for fire simulation with NIST FDS.

I started playing with the idea of transforming my huge addon into an app_template. So far so good, it is quite simple.

My last remaining doubt is about how to port the addon user preferences.

As you know, an addon can easily create a preference panel in “Edit > Preferences > Add-on” by subclassing bpy.types.AddonPreferences

But I cannot imagine any way of doing the same from an app_template. I wish I could add a whole new panel in “Edit > Preferences”, but I cannot do something like:
class AppTemplateSamplePreferences(bpy.types.Preferences)

Any idea guys?
Thank you in advance

Best regards,

Has anybody got an idea?