I wrote an utility very close to your description; mostly my utility coincides with your description, but I have only Perl scripts to invoke.

Each utility to invoke has common agreements on parameters, and, indeed, parameters could be entered via GUI, or from command line, or both methods (entered in command line and then edited by afterwards in GUIby user), or without GUI - all ways of invocation are possible in my case.

GUI was implemented with Tcl::Tk, which is like perl/Tk but much more capable.

I can provide may be more details on this.

Also, http://search.cpan.org/~srezic/Tk-Getopt-0.49/ could be of interest for you as a starting point of your own way.