New ISO generated, with the trick of Salinko and this flashplugin. Flash works, but no more in the list :

It's a little bit cheat, but... 
- i have remembered this post:
ssx (instead of gksu) as su/sudo frontend, though not a Qt utility, doesn't depend on GTK either freeing me from another GTK cruft. Yet Octopi can't be used with it, you can use pacmanxg instead of octopi.
but i am not sure, whether it is a good idea to kick out octopi...
- i am pretty sure that lxappearance is just a system setting to change the theme/icon. if other system setting tools can do the same job, you can get rid of it.
- you have still exo installed. it is required by xfburn. i think you can safely remove it.
- libxfce4ui is required by exo. if you do not need exo you do not need this package anymore.
- gtkhotkey and libunique are required by synapse.
- gtkmm is not needed by any programm (at least in your current public lxqt image). i do not know, why it is installed.
- libglade is required by pygtk. pygtk is required by python2-notify and pywebkitgtk. python2-notify is not required by any program. pywebkitgtk is required by manjaro-welcome.
- vte is required by lxterminal. you can probably remove it without any problem.
so, manjaro-welcome and octopi are dependent on gtk2. thus, synapse, libreoffice-installer, and gparted are also dependent on gtk2. i do not recommend to release lxqt without these great (mostly) manjaro tools.
what is your opinion about that?