I learned to live with clubroot on my last plot (luckily my new plot doesn't seem to be affected).
As you say, it only affects brassicas and certain brassicas are more prone to it than others. There are a few clubroot resistant varieties of cabbage, caulis and I believe there will soon be a clubroot resistant brussel sprout unveiled! Kales, because of there tight packed cellular system have a bit of natural resistance to it and I found that autumn sown brassicas were less affected, suggesting to me that the clubroot fungus doesn't thrive in cold weather? Keeping brassicas off the area for twelve years, as recommended, isn't really a viable option and I would prefer to tackle it head on and treat it as a challenge! Starting plants in pots gives the roots a head start and a chance to establish before getting attacked!
Good husbandry will stop you from getting it if the plot is clear of it, crop rotation, not allowing weeds to grow as some weeds can be host plants,growing your own brassicas from seed helps, washing and sterilising pots etc!
I have grown Kilaxy this year which is a clubroot resistant cabbage variety, just in case I had clubroot infected soil, which I now believe I haven't, but mainly because it is a good hearty cabbage which tastes nice and stands well!
