1) firstly I would expand Tornado Ally, Possibly build Roller Coaster in that area, may be a small resturant aswell.
2) add another famliy ride in craftman's vally on oppisite side behind the wagen makers barn.
3) I would build another themed area just passed Thunderhead Gap possibly, a snow theme or fun in the sun (beach area)!
Now I'm curious on what you have in mind ti improve Dollywood. Whats on your mind?