More land means more resource and a larger population. Furthermore, the world will not object if Ukraine takes a little bite out of the monsterous Russian Federation. Since Odessa and Crimea are also not ethnic Ukrainian lands, perhaps we should return those to the Turls and Tatars. Most may argue, why add more unwilling Russian's to Ukraine. Nevertheless, most of you know too well that about half of the current population in Ukraine is Russian speaking.
More land means more resource and a larger population.
Furthermore, the world will not object if Ukraine takes a little bite out of the monsterous Russian Federation.