[] Sinecure
The first possibility, of course, is that you accept the current status quo as a reward for your hard work, rather than a deficiency to be addressed. Belegar will keep finding ways to make use of your talents, and you'll have time and resources enough for your pet projects, as well as still being on hand should something go drastically wrong and need correcting.
[] Loremaster-at-Large of Karak Eight Peaks
Or you could push Belegar to continue sending you afield. He does want to continue to enhance the stature of Karak Eight Peaks in the Karaz Ankor, and what better way to do that than for you to travel it and solve all their strangest problems? It would also mean getting to see every corner of the Dwarven world and encounter all the strangest phenomenon it would have to offer.
[X] The Waystone Project
Or you could turn to the biggest possible project you could pursue. The Laurelorn Elves have voiced their desire to work with you to unravel as many secrets as possible about the network in the slightly inaccurate belief that you already have some of those secrets. This might be the only chance to pool the knowledge of the Laurelorn, the Empire, and the Karaz Ankor, and for a project that could do wonderful things. Sure, you doubt you'll be able to replicate the combined efforts of the Elves and Dwarves at their heights, but every scrap of understanding of the existing network could make all three peoples better able to protect and make use of the ancient energy streams.
[X] Markgraf of Eastern Stirland
A Markgraf exists to transform troublesome land into a land of productive and obedient tax-payers, usually after said land has been conquered. Historically, it also apparently exists to create rivals to the Elector Count that appointed them, which is probably why the letter made it so clear that no inheritable position would accompany the title of Markgraf. It still remains a position of extreme power, prestige, and influence, second only to the Elector Counts themselves. And it would be quite a feather in your cap if you could one day boast to have pacified Sylvania.
[X] Count of Sylvania
Or you could go even further with House Weber and turn them - well, turn you - into proper aristocracy. One slice of Sylvania would be significantly easier to pacify than its entirety, and rulership in this corner of the world seems to have worked out quite well for the former Countess of Nachthafen.
[] Spymaster of Wissenland
Grand Count Konstantin von Liebwitz of Wissenland is known to be quite touchy about his independence, so when you spread word that the Skaven were in a civil war, he lead the forces of his county against the Skaven stronghold of Under-Nuln without any outside assistance except a single Dwarven diplomat. It went rather poorly, as the Civil War had already been decided there and what he had taken for continued fighting was mere squabbling over the spoils. Reading between the lines of the offer, it seems that there may be further consequences for that failed attack, and Wissenland wants your help to avert them.
[] Ambassador-at-Large to the Karaz Ankor
An Ambassador is appointed to a single polity, whereas an Ambassador-at-Large has broader rights for many more places. In this case, for the entire Karaz Ankor. A prestigious and important position, and one that might be a stepping stone into even greater positions within the administrative infrastructure of the Empire. You may not be quite as diplomatic as other candidates might be, but you pride yourself on your understanding of Dwarves and your reputation amongst them is, to put it mildly, rather good.
[X] Bodyguard and Tutor to Prince Mandred
Though the offer came through the Chamberlain of the Imperial House, this has Heidi's fingerprints all over it. You're not sure if the offer is for exactly what it says or as a cover for beings her catspaw as she plays politics, but either way it would be a position extremely close to the levers of power, and one that would let you have a huge amount of influence over the likely future Emperor.
[] Governor-General of Swamp Town
This one is an oddity. The others, you can follow the logic as to why it was offered to you, specifically. But why Swamp Town? Are things there so drastic they need a powerful Wizard to get it under control? Is something particularly magical going on there? Has it become a haven for Black Magisters? Whatever the case, if you want mysteries and adventure, there's few places like the New World for encountering both on a regular basis.
[] Ranaldian High Priest of Kislev
Another one from Heidi, this one more directly. This is a wheel you set in motion yourself, and perhaps it's suitable that you follow it through to the end, resolve the grudge between Ranald and the Gods of Kislev, and establish the worship of your oldest friend in a new land. You did leave quite a few mysteries behind in and around Kislev that you'd quite like to get to the bottom of, and it would be fun to have the undeniable right to attend future Grand Conclaves.
[X] Border Princess of the Howling River
With Karak Vlag returned, the only pass through the World's Edge Mountains that is not dominated by an existing Dwarfhold is Mad Dog Pass. It seems that Barak Varr wants to change that. Many have tried to make something useful of the sprawling, anarchic lands known as the Border Princes over the year, and one of the few times it was managed was almost two thousand years ago, when Emperor Sigismund the Conquerer established the province of Lichtenberg. With Dwarven support, perhaps you can follow in his footsteps.
[] Nagarythe
For delivering a Druchii that had been working with Clan Moulder to the Nagarythian Ulthuan Ambassador, you were given a token that will allow you to live and fight alongside them for ninety-nine days. There's no time limit on it except for your lifespan, all you have to do is arrive in Lothern and present the token. You did just complete quite an adventure, but perhaps that whetted your appetite enough for another.
[X] Research Sabbatical
You can't deny that your research projects have been piling up, and it might be nice to take some time off to concentrate on getting through those. But it would mean no immediate challenges to keep you engaged, no employer resources to draw on, and no payroll to keep the Wizards you've gotten used to working with around and focused.