If you think Tua has a chance to be a very good to great QB it doesn't matter who else is there. A QB is so much more important to the success of your team then any other position that if you have a chance to a get a franchise guy you don't pass.
A QB is like a pitcher on a baseball team, they have a bigger influence on you winning and losing then any other position and its not even close.
A "healthy" Tua would be the number one pick a lot of years. You don't pass on that hoping to get Trevor next year. There is no guarantee that you are going to be that bad. Franchises can go decades without getting a top pick, if he is healthy you would take him. Honestly though if he makes it to 7, there is a reason.