It is true that adding another check (for level) along with the already checks would be bad design, especially at such low numbers of Merc (would probly work fine with 600+ active mercs spread across all levels).
But it is also true that those on high maps (especially swamp) are a bit more safe compared to rest of maps, which is also something that we don't want.
So, in order to prevent a bad design and also fix such "safety" in high level maps, we'll add a new feature that will set the mercenar level to the same level (max 380) as the target during quest time, similar mechanism that we created for IT level adjustment.
In this way, any map will be accessible for the quest no matter where the target is.