Mafia 44. Time of Troubles

On the one hand, you're right, but on the other... What if they turn out to be too strong? Besides, the Monk could die on the first night, and then they'll have a clear advantage!

Winning through conversion is quite difficult in itself because you need to convert many units. Also, they won't be recruiting to their own side (meaning the player won't be playing as the Lithuanians, they'll just change their allegiance).
I wouldn't call the presence of a Monk such a strong counter to the Incubus. Both neutral units are hidden, there are many players, and you need to target them precisely.

The most important thing here is what you want the Lithuanians to be:
a mafia with a non-standard win condition (and possibly a different play style) or a mafia with an additional win condition (because nothing prevents them from classically eliminating all other factions).