Greetings, Wood-Elf.
If the Crown would come into the possession of the Empire, it is our intention to first and foremost lock it up in the vaults of the Pyramid of Light, where it can do no more harm. We'd call together a Council of the Wise, with representatives from every one of our allies and friends, and from the races who know more about these arcane things. Only then can we decide what shall happen with the Crown. It is entirely possible that it will indeed be given to the Dwarfs, but we cannot decide such things on our own. The Dwarfs were, after all, the race that made this trinket and then failed to destroy it once already. On the other hand, we will not wage war against the Dwarfs if they give us no reason to by attacking us first, for we do not forget they have been allies since the dawn of our empire.
OOC: As said before, we do not want to attack the Dwarfs, neither do we like the storyline GW has set for us all that much. But, we're keeping to what seems us the most probable way the Emperor would deal with this item. Just handing it over to the Dwarfs after they marched into our lands bearing arms and without warning, seems not very probable. On the other hand, it's also entirely improbable that he'd want to use it, and corrupt himself by doing so: that'd make the Empire shift to an evil nation, and I can't see GW changing the Warhammer world this much.
Is this acceptable to you? Of course, if you should choose so, we will welcome your representatives to a Council as described above, should the need arise.
Count Heydrich Starkhof