It's basically just moving a single trapping from one to the other, I don't really see a problem.
No, I get that. It is definitely a valid stunt. I had just never considered moving a trapping that affects a stress track before.
It's just that endurance doesn't have a lot of active uses. You could leave endurance, and presence for that matter, unrated then take stunts to move the Fortitude trappings to you apex skill. That gives you maxed out stress tracks and extra consequences
and it frees up two skill slots at Great or higher.
While we are taking things to extremes, you could also throw in the Hunger stress track too. But since hunger comes from a power it may not be within the scope of a mortal stunt to mess with it.