Ouch. I assume Adremelech Warlock (e.g. no non-flame basic melee attack). Not a single creature without a flame-based attack? And no fliers to at least take out the sniper?
I have done a Force Push + Maim Wings to the Lord of Fire before.....
Cool trick, but turn 3/4, surely the Warlock has a Dispel, and almost certainly more Dispels than the opposing mage has Maim Wings. Also, you could throw a Nullify or similar onto Adramelech before sending him over the wall.
I was thinking that as long as Adremelech scores a burn token on something, then your Wildfire Imps could teleport across, but alas, they require LoS for their teleporting ability (unlike Gray Wraith, for example).
Perhaps this is a good excuse to add Eagleclaw Boots to the spell book?