Can you design in it such a way that it only downloads the model if the user specifically enables that feature? Add a note along the lines of "A one time additional download is required to enable this feature" or some such, and I think it would allow you to expand the features if you wanted while keeping the initial download smaller. I might be weird in thinking this would be acceptable. Also, would be appreciated that I didn't download something I was never using.
Long-term I'd like to support this, maybe by letting users add/delete models as needed.