I completed the improvement of the panel applet "keyboard layout switcher".
You can see a snapshot of the final version here: http://postimage.org/image/jx2nu2yip/

The features are:
- change keyboard model clicking on button and choosing from a list
- add / remove keyboard layouts choosing from a complete list including the variants
- move the existing layouts up and down so changing the toggling sequence and the default (first) layout
- change layout toggle/switch option clicking on button and choosing from a list

The source code is here http://code.google.com/p/giuspen-lxpanel-0-5-10/source/checkout

I started my work cloning the 0.5.10 version of lxpanel, the only changes that I made are to

As you can see from the screenshot, not all the flags are available.
The flags are in lxpanel-0.5.10/src/plugins/xkb/flags/*.svg and are taken from xfce4-xkb-plugin.
If anybody would like to help me complete the missing (svg) flags please contact me.

I would be very glad if my work will be accepted in the lxpanel main branch.