::Presumably it can just do something like this? 
 ::*Find tomorrow's TFA using something like: [[Wikipedia:Today's featured article/{{#time:F j, Y|+1 day}}]] 
 ::*Check to see if the blurb uses .  If not, stop. 
 ::*If yes, then find the file name (TFAIMAGE doesn't use a "File:" prefix but hopefully this won't be difficult to overcome) 
 ::*Check to see whether the file exists at Commmons.  If not, then the file is locally hosted and automatically protected.  Stop. 
 ::*If yes, then check to see if the file is fully protected.  If yes, then stop. 
 ::*If no, then issue alert. 
 ::The question of image vandalism while the blurb is still in the queue is a slightly different issue, but AFAIK it hasn't happened yet, whereas alterations to images that should have been protected but weren't has now happened.  If we can address one problem first, then we can see if we need to prevent something else!  In any event, vandalizing an image earlier in the process would hopefully be spotted well in advance of the blurb reaching the main page (not least because it's rare for an image to be used in a TFA blurb that isn't also in the article, so changing the image would change it in both places).  Thanks,