It's (literally!) called the 'Stormtrooper effect'
. It basically means the story protagonist needs to stay alive at all cost. There even have been some in-universe explainations for this...
Luke once said "I can't see a thing with this thing on." And several sources mention the rifles the Stormtroopers use are just badle calibrated. I guess the Emperor wanted to buy some cheap guns so he could save for his beach house
(history lesson mode=off)
Aaaaanyways...powers I'd like to see are Force Speed, Force Heal (or a trance), battle Rage and Force Crush. Although braking a poor Stormtroopers spine might not be good for the PG rating. Oh well...throw in a couple of Ewoks then