Instead of having to dig everything up in language files while browsing the forums (which is a time-consuming process because you really need to be able to see the text on a live board when doing a proper translation), there would be some sort of 'debug' mode for admins which would load up the board as usual, but every text on the board that is listed in the language files could be changed on the spot in some way: either a pop-up when clicking on the texts, or a small box next to each text that could be altered.
It would be really nice to be able to change stuff in such a 'debug-type' mode on-the-fly, while browsing the board. At the moment it's basically a case of browsing the board and having the CP opened up in another window and searching for the strings as you go along. Sometimes everything is neatly listed in a single file, at other times you have to dig through more than one file to change everything on a given page. Sometimes the same phrase is listed several times in various files and you have to check the url's to make sure you're not editing the wrong one by mistake.
Overall it would be great to be able to customize all strings by having them available for editing in some sort of special viewing mode that could be toggled for admins.
Just my two cents on what would be the ideal way to customize/translate a message board. Can't think of anything easier or more comfortable than that...
