Was thinking about filling the gap between the Wooden Idol and the Nordic Temple, without having to build christian chapels. Maybe a Runestone? It would need a boulder and a looot of (carving) work, and would work as pre-7.1 Wooden Idol (boosting happiness besides being an idling location). To balance it, there could be a limit of them (there aren’t that many runestones after all) and only a small radius of its effect.
Nice thought, with the limited amount of boulders in early game plus small circles it should be possible to balance it, better than with the unlimited wooden idols. I will make a couple so we can test it.