Hi,
Given that all the Jpeg will have to be rendered into 8 bit before it will play there may not be any saving as you will now have the jpeg AND the 8 bit material on your disc. This will be an incredible pain as you will have to render every time you want to put a Jpeg shot in. Not a good idea.
If you have to capture a great deal of material and then will edit with only a small amount of it there may be some space saving.. I don’t recommend what you are proposing as it will just be a big pain.
Either buy a drive or just start over would be my suggestions….
good luck..
jason