This is just a small idea I had while thinking about Chaos. We know that WOC is getting a rework for Game 3 which should make them fun to play, but we do not know the specifics of the rework. It is likely that there will be the usual things in a rework such as new starting positions, the LLs being separated into their own factions, etc. However, a core issue for this race is the roster which lags behind nearly every other race. Its unlikely that the rework would give all-new units for WOC (barring a Lord Pack that comes out alongside the rework) but a potential work-around could be found.
Case in point: Sigvald. Sigvald is dedicated to Slaanesh so it would make sense that he would have access to a small selection of Slaaneshi daemons for his faction such as Daemonettes. It would be similar to Allarielle's faction where she was a HE lord but had access to a few WE units like Dryads and Tree Kin. If Sigvald had a similar system and the right units were chosen, he would be fun and different but would still be balanced enough to where he couldn't steamroll the map super quickly. Hell, any other WOC Lords that are added through potential DLC could have access to a few daemon units, such as Valkia being able to field some of Khorne's daemons. This would not only fit thematically with WOC but also help boost their roster and make them a bit more viable.