Can I approximate stock using gelatin, MSG and water?
Yes, you can do it and it will work.
In fact, there is a huge market for products doing exactly that. You may know them as &quot;bouillon cubes&quot; but they exist in versions other than cubes, such as powder or liquid. They are a combination of MSG and aromatics, usually also salt. They rarely use gelatin, since the gelatin is actually a side effect of making stock and not necessary for the taste, but there are a few products which include thickeners, if you prefer those.
So, if you want to experiment, go ahead, if not, you might find it more convenient to use an existing product that has been formulated so it &quot;just works&quot;.