It would be nice to add an option in page [[Special:EditWatchlist]] which will help selecting all redirect pages, and one more option for non-existing pages (red links), for an easy mass removal from user's watchlist.
Specific example:
I have over 10.000 pages in watchlist in some Wikipedia, and about 20% of them are redirects, so manually it's hard to find, select and remove all such pages.
This feature is very necessary for active wiki(m|p)edians.