A change I would love to see is
Keen Eye being made into an ability that prevents the opposing Pokemon from using any move known by the user. Because the Pokemon is well-versed with a move, they are able to see it coming when used against them and can avoid or stop the move using that knowledge.
Essentially it becomes an automatic
Imprison similar to Magic Bounce but far harder to use and way more situational.
This would give the Keen Eye birds a niche unique to them as well as a certain Poison/Dark-type and a keen-eyed boxer we all know and love.
For instance,
Swanna armed with any combination of Scald, Hurricane, and Toxic now completely blocks those moves on switch. This makes her an amazing switch-in against Rain as she walls Defensive Politoed entirely and blocks Hurricane which leaves Tornadus with only Focus Blast & Hidden Power to hit her with (following common Tornadus sets.)
Hitmonchan completely blocks Close Combat and Rapid Spin meaning it not only deals with Terrakion expertly, but it can try it's hand as a Spin Blocker that can Rapid Spin itself.
Skarmory blocks Stealth Rock or Spikes from being set up just by coming into battle.
Drapion now blocks Earthquake upon entry so long as it carries the move, which lets it be the Pursuit-trapper it was always meant to be. It can also run a SubSD set that locks SubSD Garchomp out of 3 of it's 4 moves. A forgotten Pokemon turned very volatile.
It's a small change but it would make a few Pokemon pretty cool to use. I was thinking of
Unnerve doing the same thing but it's totally an afterthought as far as I'm concerned. It basically makes the opponent too afraid to use the move.
Ursaring blocking Close Combat, Stone Edge, & Earthquake to lock-down it's counters at the cost of Guts/Quick Feet.
Tyranitar...nah he really like his Sand Stream.
Haxorus blocking other Dragons from doing jack squat by having Outrage, Dragon Claw, or both. It comes at the cost of the ever-useful Mold Breaker however.
Galvantula...is actually still really bad but I hope you get my point.
I always thought Imprison had a lot of potential but the Pokemon that get it can do absolutely
nothing with it bar Landorus & Stealth Rock so it would be really cool to see the concept of the move shine on Pokemon that can make use of it.
Reference:
http://bulbapedia.bulbagarden.net/wiki/Keen_Eye_%28Ability%29
http://bulbapedia.bulbagarden.net/wiki/Unnerve_(Ability)