Unfortunately that wouldn't help with a whole lot. The danger with input is that it could be used to e.g. escape a SQL query and delete your database. Which is

Unfortunately that wouldn't help with a whole lot. The danger with input is that it could be used to e.g. escape a SQL query and delete your database. Which is why we now have parameterised queries and such to help alleviate those worries. If you think about it the process you're describing already happens: the browser sends the user's input as (usually) UTF8 string data, then the server decodes it. Changing that process to base64 wouldn't change much.