From looking at different sources about stocks and broths, I understood that the main goal of simmering the bones for a long time is to extract as much gelatin and glutamate as we can from them. So I was wondering if it would be possible to approximate stock by just boiling water with appropriate amounts of gelatin and MSG. Would this work? Maybe I could boil the aromatics like mirepoix in the water along with the aforementioned ingredients. If there is any research into this subject I'd be glad if anyone could share it with me.
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 "bouillon cubes" 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 "just works".