I have no prior allegiances other than the Mariners, so that doesn't enter into it, except that I would be physically incapable of rooting for any team with which the Mariners have ever had any bad blood or play-off competition against.
The latter rules out the Astros, Rangers, Angels, Athletics, Yankees, Orioles, White Sox.
I also cannot and will not root for any team from California because California is evil.
Buh-bye Giants, Dodgers and Padres
As for dynamism...I am referring to a club that has many different ways to beat you and players that flash unusual skills often. Best targets: the Cubs, Cardinals, Rays, Red Sox
From that group, I'd probably go with the Red Sox to please my wife...who hails from Boston.