My avatar is the Walking Graveyard, a Risen defensive structure from a yet-to-be-realeased Risen civilization in the Heaven's Fall mod.
I made a little pack for you that you can get here if you want to use it, but please give me credit (and maybe credit worldtree91 for the idea too!)
I think the pack should have everything, although I'm on a linux machine and couldn't check with the editor if I had the right files. The basic idea is this:
WalkingGraveyard model has a Sprite First attachment point, you can put a SkeletonSmallBack attached to it, and then have the WalkingGraveyard model do its throwing attack animation, and have a Sphere ability that makes the skeleton disappear off of its back mid-attack. That way, it appears to throw the skeleton off of its back. Its projectile art can be "Skeleton_Missile" (I think I got the right one of the developmental model versions, let me know if it's off) and then when it lands you can make a skeleton with the "SkeletonRoyal" model which will make it appear between the missile death and unit birth animations that the thrown skeleton busts to pieces (we have it to AoE damage) then forms back together into a unit that can fight for a short duration.
Or, you could just use the WalkingGraveyard model if you want to do that too. It's "Attack Alternate" is more normal, it just bashes stuff with its spider-half.