I don't think Tomcat has the capability to unzip request information. What type of requests are you making that would be large enough to benefit from such capability?
Take a look in the java.util.zip package for classes that can handle GZIP encoding.
Seems to me a Filter that can look at the headers of an incoming request and substitute an unzipping InputStream when needed could be used without any modification to actual server code. There are plenty of filter examples around - but they mostly deal with zipping the output to the response.