The addition to Web App Manifest is going to be a little more complex. The WebApp manifest 'icons' member is currently defined as a set of ImageResources, each of which is of (MIME) type "image" - there's a loading step that it iterates through. Unless the model type starts with "image", which doesn't make sense, it's going to be a little challenging to have mixed types in that list.
The addition to Web App Manifest is going to be a little more complex. The WebApp manifest 'icons' member is currently defined as a set of ImageResources, each of which is of (MIME) type "image" - there's a loading step that it iterates through. Unless the model type starts with "image", which doesn't make sense, it's going to be a little challenging to have mixed types in that list.