Achieving a command has a lot more to do with the attitude of the candidate than just the flying skills. People fail command checks usually because of a lack of preparation and/or the failure to change the mindset from support pilot to PIC. Plenty of people with lots of hours have failed command checks. If they are not up to the hands on skills then they won't get through the sim component but in my experience the younger pilots are good at flying the simulator. If they put the work in and understand that they are now the person responsible for the entire operation of that aircraft from stepping in to stepping off it then they should be fine. If they still think they are the head prefect of senior school then they will have difficulties.