Both of these are indeed possible, but it will require some complicated work, some of it 3d. I only know how to do this in maya.
For the ring, you'll need to create a new mesh that will act as a container for the Effect_Loc_1. You can then add an effect to a user's hand by adding that 3d mesh and the effect to the ring's artdef. (edit: planning ahead, it would probably be a good idea to create at least 4 different locations, if not 8 including the left hand. That way you could have one location reserved for flames, one for poison, one for cold, one for lightning. Although the size of these effects will be extremely small in-game, it will still look odd if they merge together in one location if a unit wears several items with the effects from different rings)
The process for the horse will be the same, although it will be a lot more time-consuming to get right.
