This manga is sweetness and wholesomeness, and that is all that it wants to depict itself as. But in reality it shows hints at a much vaster world then the sliver we are shown and also a much darker world.
The real question is whether Kazutake plans on delving into the darker parts that they hint at. If they do, this could be incredibly interesting. If they don't I feel like the Slice of Life will become dull quite quickly.

From what is shown in the first volume of "Saint Cecilia and Pastor Lawerence" it comes off as a run of the mill humorous slice of life Manga. But if it just continues to be just Slice of Life and not capture it's fantasy background I don't think it will meet it's full potential.

I am very hesitant to continue this because of just that.