Coercer and Inq are more fitting in Melee based teams, as they buff melee DPS and debuff physical mit.

All in all, you could get away with using a Coercer and Inq instead of Illusionist and Templar, but if possible I would just trade the Illusionist and keep the Templar.

But you're right, when it comes to doing city writs in Kunark, having all the same faction makes is much easier.

I would just go with your gut and use the Coercer/Inq. Its not going to make that big a difference with a group like that.