That's a good solution, Otakar. Thanks for bringing it up. I did use setups like that previously and in the mentioning of procedural smoke in the medieval city project I was 'hoping' for a simple point and click system. Like, whenever you click a certain area a soft circle is there, which acts as a placeholder for a cloud column. In fact I don't really know why I said it, as the principle is indeed not too hard. You may recall me asking for a soft, cone shaped column some time ago. The setup of hundreds of columns however, as you say, is quite tiresome, hence the hypothetical 'point and click' system.
By the way, you won't need the link from the PF to the input of the redirect shader (IMO). To restrict the warping you might add a surface shader under the redirecter, and blend that by a distribution shader, so the warping of the column only starts softly above the ground point.
Thanks, Otakar!