I am pleased to say that I now have 200 sermons posted on my blog Preached Sermons - see here. I have tried to post sermons on less obvious parts of Scripture and there are series on Ecclesiastes, Job, Ezekiel and I am nearing the end of one on Numbers. Check it out!
Bonhoeffer uses a similar phrase 'worldly Christianity'. It's J Gresham Machen that I want to line up most closely with. See his Christianity and culture here. Having done commentaries on Proverbs (Heavenly Wisdom) and Song of Songs (Heavenly Love), a matching title for Ecclesiastes would be Heavenly Worldliness. For my stance on worldliness, see 3 posts here.