The rescue bear! It would carry a barrel of booze around its neck as well!
this might work?
Not if you put booze around its neck. They'd be too busy trying to drink it to go rescue anyone.
But yeah, I could see different capabilities of rescuers. Make it like building destroyer, where there are 2 levels to it. [RESCUER:1] would allow the animal to assist injured/crippled/disabled but conscious dwarves off the battlefield. Sort of like being able to lean on the dog for support. [RESCUER:2] would be something like an elephant, where it is capable of lifting the injured dwarf, and would be able to carry unconscious dwarves inside. Depending on how robust the behavior was, you might end up with some silly situations where an incredibly tough dwarf lost both legs but remained conscious and a dog was able to assist him back inside, but overall I think it would be reasonable.
Also, I think things with [RESCUER:2] should have a chance of accidently causing slightly more injury to unconscious dwarves they pick up. Cause lets face it, you might train an elephant to drag the bleeding dwarf inside, but I don't think you can train him to be gentle about it.
I dont think the game would require something so hard to predicate its action. The game knows its relative sizes, strength, and weights. Friction is only other thing I can see being added to get a dragging mechanic more in line with reality, but I would be happy with flat values of the tile. So yea, with those three values it should be able to determine if the rescue animal can do the dragging.