RAW if it hasn't charged (see P3 of errata for this adition), attacked, cast or unbound a spell, or if it is not within 3" of an enemy Hero then Arch-deceiver should still be in effect. Using the Battalion ability that doesn't do any of those listed actions shouldn't remove that (I believe).
However... if you switch him for a unit already in melee then he HAS to attack (see P230 of Main Rulebook, "you cannot pass if there is an eligible unit from your army that can fight) and therefore break Arch-deceiver.
You could suppose conga-line the unit so some of the members remain outside of 3" from your opponent and you could swap him for one of them, meaning he would not be eligible to attack.
This is my take, happy to hear if it's wrong.