disk–halo (and halo–halo) mean-velocity differences

I had a meeting with Emily Cunningham (Flatiron) to discuss any projects of mutual interest. She has been looking at simulations of the Milky Way (toy simulations) in which the LMC and SMC fall in. These simulations get tidally distorted by the infall, and various observational consequences follow. For example, the disk ends up having a different mean velocity than the halo! And for another, different parts of the halo move relative to one another, in the mean. Cunningham's past work has been on the velocity variance; now it looks like she has a project on the velocity mean! The predictions are coming from toy simulations (from the Arizona group) but I'm interested in the more general question of what can be learned from spatial variations in the mean velocity in the halo. It might put strong constraints on the recent-past time-dependence.