Don't readily buy into every theory you hear. Bungies story presentation via grimoire cards leads to some pretty vast swings in interpretation and speculation (which I personally like). The strict grimoire version of who is Dr Shim, is he is one of 4 Ishtar scientist who during the golden age before the collapse, were involved in a vex research project. Their project resulted in new technology, where the 4 scientist took copies of their minds and put them into the vex network. Later, some of the other project members (not Shim) went into be involved in other projects, such as Maya and the Device, which you can read about in vex 5 and the Future War Cult card.