Good point. So if Trump were to pick DeSantis or Rubio for VP, I guess technically the FL GOP could put someone else's name as the Republican VP on their ballots. But the problem with that strategy is, end the end when all EC votes from all states are counted, then we could end with Trump for prez and a Dim for VP (if the Dim VP won a majority of EC votes from other states, or if the Dim-controlled Senate picked the Dim VP as per the Senate picking VP when there's no majority from EC votes).
So in the end, we're still talking about it being very unwise for Trump to pick a fellow Floridian for VP.
Yes, there are various problems such as you describe, with picking a vice president from the same state as the Presidential nominee.
So as a practical matter, presidential nominees and vice presidential nominees are always going to be from different states.