Dwight Normile makes a convincing case:
… Even if I don’t agree, I can understand the limit of two for apparatus finals.
But two per country in the all-around is too severe, especially at a time when all-arounders are a shrinking population. At the London Olympics, for example, only three men’s teams had more than two all-arounders. Two-time world all-around silver medalist Philipp Boy was among those who got bumped. Of the 12 women’s teams, six had three all-arounders, and six had two. 2011 world champion Jordyn Wieber was eliminated.
The individual all-around used to be the centerpiece of a major championship. Eliminating potential gold medalists, such as Boy and Wieber, tarnishes that title. …
The FIG Executive Committee can keep the two-gymnast limit for event finals, but it should return to three gymnasts per country in the all-around …
IG – Stretching Out: Is It Time to Drop the 2-Per-Country Rule?
I slightly prefer 2 / nation. But could live with 3 / nation as Dwight recommends.
In addition, if 4 gymnasts travel to a World Championships (e.g. Antwerp), all 4 should be allowed to compete on each apparatus, if the nation chooses to do so.
Al Fong: … fans’ loss that Brenna did not compete.
Gymnastics Coaching.com 