I think it would be really cool to be able to set some kind of viariable that sets a slowmotion effect, but also allows you to choose which sprites and other objects are effected. Imagine if there was a little tick box in the properties of any object or movement behavior that said "is effected by slowmotion"...and if you checked this box, suddenly you could set the slomotion variable to any percentile value and those objects would automatically animate that much slower, move that much slower, and most importantly even the movements like platform movement would behave slower.
This would allow for amazing effects for drama or even for gameplay..like a weapon that slows down (or stops) time but not on the player...It would also be a powerful way to allow for a game to be paused with custom menu's and such...just set the slo-mo variable to full stop.
I know things like this can be achieved with careful programming, but wouldn't you have to create custom movements for it to work perfectly? If this were built into the engine it would really help game makers (even ones with poor programming ability) make drastically more dramatic games.