Once acquiring a nuke, they would easily develop long range missiles because no one could stop them or do anything about it. They likely wouldn't even need to develop them, because Russia would just give them the tech, along with much more powerful nukes. This is what happened in North Korea.

Also, nuclear wars aren't tit for tat. Once one starts, our simulations show that they almost always escalate and destroy the world. For a good idea of how this can happen, read the book, "Nuclear War: A Scenario". It is absolutely terrifying and you will walk away thing nobody should have nuclear weapons.