The big problem with this is that the code doing the searching has to run on the server because that's where the database files are that hold the posts. As such, searching would put an enormous demand on the servers - much more than they could feasibly handle. To move the load off the server, we'd have to have verbatim copies of every post in another location that was able to handle the load. It's really not a matter of writing the code; lots of people can do that. It's a question of getting access to the data to search, and having the CPU power to run the searches.