If you are interested in ideas for a stunt dummy for aiki katas...
This type of uke is more challenging than one may believe (and don't assume it's not intimidating once you're in action "against" it) - the amount of mistakes you can make with this uke only is amazing.
Occasionally, it is even more serious than some ukes in some dojos
A ladder, Duct tape. Tondoludos (from aquagyms). Big gloves. Plastic weapon.
Cons: can't move, wrist is rigid.
Pros: lots of katas, intensive training options.