assuming we keep the majority, need to elect a new President pro tempore. Maybe a younger guy and someone who wont even think about the 25th amendment.
I agree.
You would have to elect a new one because Hatch is the current one. The President Pro Tempore is usually always the senior member of the majority party (though not by rule but by tradition). In this case it would be Thad Cochran assuming he does not resign by then - next in line would be Chuck Grassley.