I'm terribly sorry to say this but you're all horribly wrong and didn't really think about how you were posting "no u cant do dis its imposibl" when you really didn't know if it was possible and you knew you didn't know. Uh, sorry.
It
is possible to make what is random for the purposes of gameplay, and it only takes two shifts and one tile.
STEP ONE: Place two different shifts on the same tile. It doesn't matter which shift ID's you use or which layers you put them on.
STEP TWO: Set them both to shift on touch, set one to the Spot shape, and set another one to the Circle shape. Assuming you don't want your players to think "oh god what is that horrible animating piece of crap over there, I guess it's a couple of shifts both on the same tile for some reason, maybe I should step on them," make them invisible.
STEP THREE: Go on ahead and set their destinations/flags. It is important that they
do teleport the player away.
STEP FOUR: This is very important. Make sure that the pair of shifts can only be approached by walking/running into it. If the player jumps up into it, or falls onto it, they'll always trigger the Spot shift in the first case and the Circle shift in the second.
What happens is: when the player
walks into the shift, if the Circle shift is in its largest animation frame, it is triggered, otherwise the Spot shift is triggered. If they run, then the cut-off point is in the middle of the animation. But this
only works from the right side. If someone walks in from the left side, the Spot shift will always be triggered. Running is better but probably pretty useless.
This means a 1/(frames in Circle animation, which I believe to be 6, but the animation is contained within KS itself, and I'm not downloading the MMF2 trial just to find how many bloody frames are in a bloody animation) chance of the Circle shift being triggered,
if the player is walking. (If the player is running, it seems very close to 1/2, which is nice, but I'm not sure.) If you want a different chance - and indeed you probably will - you'll need to use multiple screens, which is just as awkward as you'd expect in terms of gameplay.
Now, this isn't a random choice, and someone with a ludicrously fast response time could potentially manipulate the result (as could someone who uses a crappy computer or CPUKiller-type program to slow down KS), but
for all practical purposes it is good enough.
The main problem is that they have to walk/run into it, it can only be from the right side, et al. It is very difficult to incorporate seamlessly.
Is this confusing? Probably! That's why I made an example level for it!
Download it here, if you must.