I suspect (having been there and done that - spent some time on early EFA HUD before switching to flight controls), that as wide a focus as possible might be best for saleability. There are good books on taking an aircraft through from concept to flight (I'm thinking in particular of one on the 777 based on the C4 series) covering the full range of development. But instrumentation alone is getting a bit narrowly specialised, you would really want people right across the project. Or, you would want to cover multiple projects if you keep it narrowly to instrumentation.