Could you not RemoveType then simply AddType again, but pointing to 5.3 this time?
From the Apache documentation: "RemoveType directives are processed after any AddType directives, so it is possible they may undo the effects of the latter if both occur within the same directory configuration."
Also, I'm not sure exactly what I would AddType. I believe that 5.3 is compiled as an Apache module, that's why the parent directory was forcing php 5.2 to run as a CGI script. So I would imagine that if I could just unset what was set in the parent directory then the default settings should kick in. Admittedly, however, I'm not all that knowledgable or experienced when it comes to this stuff.