Aren't enough specimens to go around, every craft which has taken to the sky has some modification or other and is being used to validate the adherence to some parameter or the other, even if TACDE got heir hands on the bird now it would still take an appreciable amount of time to get the job done. As for the sim, its not a matter of how much time it will take or the capability to realize a sim but rather an absolute lack of foresight, the folks at ADA have treated this whole thing as a science project, to design a good flying machine not a feasible war-machine. What we are now seeing are the corrective measures being taken to mitigate that early thought process and POV that drove the project so that an employable and maintainable war-machine can be handed over to the IAF, ergo the delays.