I've got same situation here, good thing is, that in this playthrough i have husband with his own city, so i can stack best top tiers there for free.
Easy way to start war without honor hit is to join ongoing battle, the only thing getting hit here are relations, easier to come by than precious honor. Unless you find faction mercenaries. Downside is that the faction which has been attacked will offer you peace really fast, since they want to fight against previous foes without any more disturbances from other factions. You will have to do that first battle near settlement with ladder siege, with 2h building time you might be able to get their fief before they notice whats going on. Or just start rampage and catch a few nearby lords to startle them enough to pursue the war a little bit further.