Ok, yeah I guess it might slop around a bit in transit (or Ducato, even
), but the seal's not going to be soaking in it, and it's a diluted amount.
I know many who have been using bio liquid or tabs for quite some time and haven't heard of anyone needed to replace damaged seals yet. And even if they do, I suspect it'd be after several years, and the seals are pretty cheap, and (apparently, cos I've never had to do it) simple to fit.
So all in all I don't think it's a huge risk.
Plus, personally I reckon the smell of the blue stuff is just as bad as the "natural" contents of the cassette!
Steve