Use a HUD attachment to add an alternate "find" button. It contacts a central server for a database of ads with texture IDs, plus ordering and keywords. I don't know if the scripting wizards here have a way of displaying arbitrary text yet or not
but if they do that could be used for an index, and voice commands for keywords to search for.Of course the problem is a) it's a huge amount of work and it would have to be given away for free in order to gain sufficient ad coverage to be worth using, and b) effectively competing against Linden seems somewhat, well, suicidal. Still, I wonder if there's sufficient support amongst those disliking the new classified system to attempt it..