The self-organization of cellular collectives is crucial in development and cancer. Multicellular aggregation in cancer is associated with a higher efficiency of metastasis. However, it is not fully understood how mechanochemical microenvironmental cues affect the organization and stability of such ensembles. Here, using a model system of ovarian cancer spheroids, which temporally transit from solid, dysmorphic moruloids to structurally plastic, lumen-containing blastuloids, it is shown that the periodic volume fluctuations observed in blastuloids are driven by lumenal fluid influx and cell-cell junctional states. Furthermore, blastuloid cell states are reprogrammed, which enables them to rapidly recover from even complete structural disintegration and self-organize into fully lumenized ensembles. Using targeted chemical perturbations, two distinct cues are identified that regulate separate transition traits: calcium levels establish cell states cognate to, and pH regulates the fluctuation dynamics of blastuloid phenotypes. The work holds significant implications toward understanding mechanisms governing structural resilience and plasticity in complex cellular assemblies.