That's three reasons, mate.
And you forgot a couple as well, between the Revs' attack, Kuma's freedom, the introduction to the CD's personal police system, Wapol's return, Koby meeting Vivi: all of which are important for future plot, not Vivi alone.
It leads to the Seraphim, which:
-fuels more of the Lunarian plot;
-fuels more of the DNA research plot (and therefore current Vegapunk's plot);
-sets up the End War.
It also sets up Cross Guild, which will play a role in the End War.