Why is this ridiculous?
Keterys now it is you i believe who needs to reread the power. If the shift happens first, how in gods name do you ever end where the creature was, a possibility explicitly explained in the power.
Footwork Lure is the big culprit here, because it says that you "slide the target into the space you left"- even if the space you left is only one square wide, and the creature's space is four squares wide.
If you shift so that there's one square between you and an ally, can you slide a large-sized creature between the two of you so that you're flanking? What about a huge-sized creature? Gargantuan? Is it only taking up one square? If not, how many of the four squares have to fit? If the four squares don't all fit, what happens? Why isn't this even remotely brushed upon in the power's description?
You switch places with a large creature.
SO:
<<<WHAT SQUARE OF THE LARGE CREATURE DO YOU SWITCH WITH?>>>

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.