That fender rust is farther back than you think and the rockers look horrible, it all needs to come apart in my opinion.I disagree. It is the first area to go and not a leading indicator of other major problems. You can see that the rust is on the trailing edge of the fender. The leading edge is open an accessible from the well. The trailing edge is sandwiched against the structural (and very thick) lower a-pillar. Moisture gets trapped in there and the paper thin fender takes the hit. The lower A-pillar just gets pitted.
You can fix this without touching the rockers. Conversely, if the rockers are bad you need to remove both front AND rear lower fenders, as they wrap around the rocker and are welded in place..