Perhaps I'm a little off on this one.
I wouldn't have a problem if PC w/ three iterative attacks changed weapons three times. I do have a problem with a PC changing weapons more often then they have iterative attacks, which is the situation I described. Two melee attacks, two ranged attacks, changing weapons four times. That's too much, IMO.
In the example given, Frank is a FTR1. He starts w/ greatsword, switches to handaxe, then goes back to greatsword. One to many for my rule of thumb.
I also see a difference between essentially using the same weapon six times (drawing arrows), and using and abandoning different weapons.
IMO, seems like too much activity for one round. A character w/ 4 iterative attacks, I probably let change weapons as much as they want. Aragorn can do whatever he wants!
edit - and I see in my post I said 1 change/round period. So, I'm wrong under how even I would do it. I'd call it a bad day, if there weren't so many of them.