The first and most common answer to your second question is "why reinvent wheels?". I like to reinvent wheels, but sometimes it is better to spend our time on something more useful.
There are many other reasons to use CGI::Application:

• it is possible to subclass and extend C::A; I used this approach to add session handling;
• it is possible to execute pre-runmodes and change rm at run time
• you get CGI and HTML::Template objects for free :)
• there is a nice mailing list where you can post your questions and suggest improvements; online archives are here (old messages are also here)

I'm sorry, but I didn't understand your first question, so I can't give you an answer.

Ciao, Valerio