With the new Temple Guards coming out, the mechanic of them attacking faster is a clear reference to a religious zeal to make them fight harder. That’s honestly a good mechanic and suitable enough. That bonus of being able to train them from monasteries is also welcome. But I feel like some more unit/research synergy could be neat. I wondered if getting Faith could make them immune to conversion as an interesting extra bonus. Faith isn’t an exactly ubiquitous upgrade and it would give the unit another quirk.
That made me think of other potential synergies like Tarkans also benefiting from arson or other things along those lines.
And yes, I know slingers are the new anti-monk unit for Inca/Map/Tupi/Mui but it’s not something incredibly game breaking, especially considering they are shock infantry so your very affordable Militia could counter them. Either way, it’s mostly a more “for fun” idea that some more underused units could get sprinkled here and there.