The card text is a little confusing, but I see what you are getting at after reading the notes...
Maybe try something like:
"Target a creature slot. Swap its occupant with the occupant of a random slot on the opposing side."
As a side note, though, the chance to "steal" an enemy creature is not necessarily 50%. It may be higher or lower depending on how heavily populated the opposing side is.
It becomes 50% when the opposing side has a half filled field.
Of course, most likely you would target a slot on the enemy field so at worst you simply exchange creatures and at best you get something for nothing.
Alternately, you could use this to deadly effect with Novas by targeting a singularity on your side.
At worst you got rid of your singularity and gave it to the opponent... at best, you also gained one of their creatures at the same time.
Anyway, it seems pretty fun... though I have a nagging feeling that it may be OP... Even with singularity abuse aside.
I will have to think on it for a bit.