Problem: (1) Given a category of user or user talk pages, determine which have or have not been globally locked. (2) Given a page (e.g. a sockpuppet investigation page), somehow highlight accounts that have been globally locked.
Proposed solution: It is not possible to determine efficiently whether a list of accounts has been locked. It is now one API request per user, instead of the 1 request for 50 or even 500 users. Solve the API problem and gadget writers can do the rest.
Who would benefit: Stewards, those dealing with cross-wiki sockpuppets and spam, admins who deal with block appeals, etc. Also a small reduction in the amount of cross-wiki abuse.