Not sure we have enough scripting commands for that, but there are a good bit for a decent start.
SetAnimationSpeed(entity index,speed) - set the animation speed of the entity.
If you could incorporate this into a copied script for a character and in conjunction with the animation speed setting in there properties. you might be able to pull this off. Putting this in spots in the script where you want to slow things down
As I am not proficient in Lua scripting I have no clue on how to tell you to start.
I am sure some one else will chime in with a solution.
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz, 2400 Mhz, 4 Core(s), 4 Logical Processor(s), 4gb RAM, Nvidia gtx660, Windows 7 Pro 64bit