Filter Request or Reponse as part of TCP or UDP Flow

I have a large trace which only contains Radius Traffic (but could apply to any type of traffic) and
would like to do a TCP / UDP filter such as filtering out radius Traffic using the following Analysis filter:

radius.User_Name == "UserID"

But I would also like to get the responses I get back from the destination server. Something like:

radius.User_Name == "UserID" and response

Would be exactly what I would be looking for to filter on.

This would be an extremely useful feature to be able to filter either on the source or destination flows such as being able to do:

radius.code == 3 and request

Or

http.response.code == 404 and request

So that way you could take a trace of all http traffic, and then filter on any 404 error messages you got, plus then also grab the request that was being made.

How difficult would this be to add into the analysis filter?