On the first matter I'd definitely get in touch with the original developer of WWW::Tv if its just another database chances are A: He/She already thought on it and adding one parameter to the constructor would be enough to read that. B: Is willing to let you contribute by submitting a patch. It doesn't makes sense to me to write a 95% similar module. What makes CPAN/Perl rich is the community behind and I'm sure the owner of that module would love any feedback you might provide.

On the second module if it is worthy for you just write it, there will be others like you that need the same and will appreciate that someone else took care of it. Even if you end up not uploading it I think its a valuable experience trying to write a module that someone else would use and coping with CPAN's requirements for public domain modules