Since I introduced this idea, I might as well start things off...
Hengis has suffered a total and devastating loss of faith. He no longer follows Boethiah in any real "servant" kind of way. That's not to say he doesn't still have beliefs and ambitions that promote her cause; just that he's now doing it despite her rather than for her. He will need to navigate the road ahead taking account of this. Once he's got over his initial anger, he'll realise he isn't opposed to Boethiah, but their goals only align in certain places and not others. Ideally he'll figure out a way to continue without direct confrontation and resulting annihilation.
I'm going to take this opportunity to branch out a little and take on a prestige class to represent his change of direction and idealogy. He's going to become a Comtemplative, and this will manifest in him taking more direct responsibility for his actions and goals, and also becoming a little more distant and thoughtful in his demeanour. The ultimate end of the Contemplative path is to actually become an Outsider, and as he progresses he will gradually become less human and more of a supernatural being in his own right. This may well have certain implications for his mortal relationships.
Anyway, all that is a way off, and for the immediate future his priorities will be torn between securing Falkreath and making it safe from counter-attack by the Empire, and helping Thaelestra find and finish off the Hag Sons. I'll be quite open about this here; Hengis wants the job of Jarl of Falkreath. He's thinking quite seriously about asking Ulfric outright to grant it to him in satisfaction of his declaration when we gifted him the Jagged Crown. It would have been convenient if the old Jarl had died during the battle, but that doesn't appear to be on the cards. Perhaps Hengis will learn the Heal spell and manage to cure the old fool so he can rule adequately.
The main threat from the Empire seems to lie in the mountain passes, so we're going to need some way to guard them or close them. That might be a decent use for the Wish if we can word it properly.
The tunnels beneath the Keep need searching and clearing. They were called the Falmer tunnels so who knows what kinds of horrors lurk down there. That sounds like it could be another nice litle bit of dungeon delving for us. Main question is when and what other things take priority over that.
Our new ally the lich, Urdalf, is an awesome boon, as he seems to be capable, and willing, to identify our enormous pile of loot for us so we can finally do a proper share out. I'd really like to do that before we go and take on the Hag Sons, because that lot is going to make a big difference to our capabilities in the field, and from what we've seen so far we're going to need every edge we can get.
Okay, I think that's enough from me to be going on with. Over to you...