If players can earn (or purchase) double Hero bonuses, then it only makes sense to have Double Inquisitors. In fact, the argument can be made that because players already have the possibility of having 3 inquisitors (Adrian, Sixtus, and troop type) a Double Inquisitor bonus would be an obvious addition to the game.
Most players use "doubles" during KvK and OvO events to save time when trying to earn points.
Also, using a double increases the attack bonus much quicker.
Almost the same amount of points are given for killing assailants or apostates. So why not provide players a way to earn just as many points using an Inquisitor as their Hero?
And the monthly tasks for inquisitors could also benefit the use of a "double."
The above task requires the killing of 70 level 4 apostates. At one hit per 3 seconds (ONLY if the player's town is right next to the apostate), it takes a minimum of 3 minutes to kill one apostate. That's a minimum of 3 and a half hours of game play; just to kill 70 apostates.
And let's face it, it's a very BORING, tedious process.
A double inquisitor would speed up the process and provide players the opportunity to level-up inquisitors at a faster rate, potentially promoting the need to purchase inquisitor candles with more frequency.