The CE only applies when the Savage character doesn't have Savage, which is when it is within 6 of a character with Empathy. At that point, the CE may be used on the affected character. So, MM is right, where it starts is where it needs to have the Empathy applied to it. Once it has been swapped, the only reason you would need the Empathy there is if you wanted to swap again later.
This tactic makes for a fun day. :) Here are a few squads I used, but feel free to change it however suits you best:
http://www.bloomilk.com/Squad/77773/imp-rakshttp://www.bloomilk.com/Squad/53533/new-raksRakghouls using Palps Force Points is Sooo much fun...:) And giving them Cunning and Opportunist really helps them out. Combined with Tarkin, it's a quick way to get across the board as well, i.e. move 6, kill something, move THAT one, kill something, move THAT one and be across the board before your opponent even knows what's going on. With the witches in place, swapping now gives you many options. Either way, have fun with it. :)