We're going to help Ukraine rebuild their military to try to deny Russia an opening to grab territory while Ukraine gathers their forces.
Ideally, Ukraine shifts the center of gravity of their 6th Corps east to cover eastern Ukraine; shifts their 8th Corps guarding Kiev to also defend the northeast part of Ukraine; and shifts their 13th Corps north to cover the Belarus border east to the Kiev region.
I'd create a fourth corps (really division-sized units) to cover the region from Transdniestria through Odessa to access point to the Crimean peninsula.
But if there is no money for that, the existing corps will have to cover the same ground.
In wartime, 6th and 8th Corps' jobs would be to fight a delaying action while falling back intact to the Dnieper River where they would try to halt the Russians; and where they would attempt to support special forces stay-behind teams and local irregular fighters in resisting the invasion and occupation of eastern Ukraine.
13th Corps would need to hold fast to prevent encirclement of 8th Corps from the west and to keep lines of supply open to NATO.
The new "fourth" corps would have the job of preparing for offensive action in addition to holding terrain.
Plan A would be to launch an offensive into Crimea to recover that territory.
Plan B would be to launch an offensive into Russia's Transdniestria to have a bargaining chip for negotiations after a ceasefire.
And Plans A and B would include plans to launch surface-to-surface missiles at Sevastopol bases while a rebuilt navy uses small combatants with anti-ship missiles to raid Sevastopol and lay mines around the port.
And if NATO has better infrastructure and more military capabilities in eastern NATO, the threat of NATO intervention won't be hollow the next time, possibly deterring Russian adventurism.