The way you build your application is really up to you. You can include models other than .j3o. You can even do that on a production level application.
You can create .j3os also yourself by code. Just load the model and export it straight as .j3o. But that is how the SDK also does it, so the same memory constraints apply.
There is also this, it does the same. But maybe since it doesn’t do anything but that, the memory is just enough to run it: