Does it emit a warning of some sort when it's forced to use AffineTransform due to a lack of WCS key words in the file?  Would something like that be a good idea?  On the one hand, people will want to sometimes have fits files without WCS key words, but on the other hand, if they think they've defined a WCS and it turns out it's screwed up so that WCS doesn't get used, it would be useful to have a warning.