Deriving from GObject in C++

[gnu <gnu 0x1b04 eu>]

I want to make a GUI app and have only little past experience with gtk
and gtkmm. The program is actually finished apart from a GUI and is
written in C++. I thought about deriving from GObject using C++ and
create a bunch of custom classes and widgets (not only overriding
existing methods but defining new ones), that can then be used in the
wider glib/gtk world through GIR introspection. This would comfortably
open the door to using some scripting languages for the GUI part - at
least that's my fantasy.

But is this even possible and what would be the recommended way to do so?