Are cool and all but how do you get them to show up in ftp gui's? They show up fine in dos prompts and shells, but not in WSftp, possibly some other ftp clients. You'd have to enbable it on the server i'd image but I dont see a way to do so.
If the GUI client isn't configured to show the login banner in a popup, or show the 'raw' data window I don't think you can 'force' the client to view the banner.