I heartily support the idea of using our undead armies to assist the Dawi. It will do nothing but generate positive press for us, and since it is inevitable our true nature will get out eventually, doing this will help compensate for the negative malus every human nation will have.
Heck, if we do something huge, like reclaim Karak 8 Peaks or something, a MAJOR Dawi Hold, then the Karaz Ankor might, maybe, come to our aid if Brettonia invades our lands to destroy us. Its not likely to be done before Brettonia finds out about us, but its a nice dream.
Hey, other targets exist too, and closer ones.
www.gitzmansgallery.com
According to this huge map of WHF, we're not that far from the Black Chasm, a Skaven lair of some repute, and right next door to that is the Massif Orcal, which is infamous for being an untamed mountainous region filled with monsters.
The Black Chasm in the lands of Bretonnia has been a site of strife between the clans of the Skaven since Clan Pestilens returned from its long sojourn to Lustria. It was here that Clan Pestilens' ancestors made one of their earliest homes. Their ancient forebears carved out a series of...
warhammerfantasy.fandom.com
Black CHasm apparently is a point of contention between CLans Pestilens and Eshin, so if we did hit it hard and retake the area, we're hitting both of them really hard and hurting them. And we have quite a few advantages against Eshin assassination in that we're an immortal vampire, so that's a plus to sticking it to Eshin if possible (ie nobody else has the advantages we do to survive Skaven retaliation).
Drowning those areas in undead, seizing Black Chasm for ourselves, and sweeping the Massif Orcal clean of monsters, might very well on its own make Brettonia pause and reconsider us as something beyond just an inhuman monster.
OTOH, we're also planning on treating the common people better than exploited peasants, which they won't like AT ALL. Even if they like what we're putting our undead to use for, that alone would warrant an invasion according to intolerant Brettonian eyes.