Playing the Vasari on Single Player FFA on Systems Of War (which is a 5-star, 50-planet map), I eventually got to the point of having all researches and a maximum fleet. The rest of the game involved me hunting down the remaining empires on the other star systems. The Returning Armada skill began to hurt me in this regard. The Dark Armada would spawn at over a dozen planets where I had built the Phase Stabilizers for quick phase jumping. This put my fleet capactity in the negative hundreds, even though I had full fleet capacity research and there was no way of getting it back to a positive value, except scouring down all the planets with Phase Stabilizers, scuttling the Dark Armada units, and hoping I could rebuild my actual fleet before another Dark Armada spawned. The Dark Armada are nice as a supplementary defense for your planets, but they become pointless as they use up your supply. And since the Returning Armada skill is at the final technology level, by the time it is researched there isn't a need for it.

I suppose I could scuttle Military Laboratories until the last level of military research is unavailable to effectively stop the research. I do not know if there is a way to undo research, but in future games as the Vasari, I will never research Returning Armada.