Flexible Rydberg aggregates, assemblies of a few Rydberg atoms coherently sharing electronic excitations while undergoing directed atomic motion, show great promise as a quantum simulation platform for nuclear motion in molecules or quantum energy transport. Here we study additional features that are enabled by the presence of more than a single electronic excitation, thus considering multiexciton states. We describe cases where these can be decomposed into underlying single-exciton states and then present dynamical scenarios with atomic motion that illustrate exciton-exciton collisions, exciton routing, and strong nonadiabatic effects in simple one-dimensional settings.