I'm not sure there can be a quality argument made for any team's having a dynasty. It's such a rare event that any argument in favor of it is highly unlikely to prove correct.
Said differently, it's easy to simply argue in favor of it, but it would be very foolish to put any money on it. You could bet that 100 teams would have a dynasty, and you'd probably win either zero or just one of those bets, losing either all or 99 of them.
And in this situation, you'd be arguing in favor of a dynasty amid average or slightly above-average quarterback play, thus necessitating an unlikely degree of talent throughout the rest of the starting lineup, which would also need to be sustained throughout the period of the dynasty. Those are highly unlikely odds in the age of salary cap.
I'm in complete agreement that a team can win a Super Bowl with Tannehill-caliber quarterback play, assuming it can amass the necessary talent elsewhere, but a dynasty under those conditions is impossible in my opinion.
One of the major reasons New England has had a dynasty is because Tom Brady takes regular voluntary pay cuts, which frees up salary cap money to surround him with talent that other highly-paid QBs don't enjoy. Belichick of course is a key part of the recipe, but Brady's pay cuts are very important as well. New England essentially enjoys a caliber of talent surrounding its very good QB, that only teams with much lower-paid and poorer-quality QBs can have. There is only so much room under the cap, and when you pay your QB a great deal, you lessen your ability to surround him with talent.
Pay attention to what happens with the Seahawks, now that Russell Wilson is highly-paid. Also pay attention to what the Cowboys can do, having a very good QB on a fourth-round initial contract for the next three years.
