Update:
The scope is in fact bigger than previously thought: 2 other options were forgotten that need to be set only in a Unity 2D session:
/apps/metacity/general/show_maximized_titlebars false /apps/metacity/general/auto_maximize_windows true
A new simpler, more generic solution was thought by Didier: adding a command line option to metacity where one could pass a file containing a set of GConf key/value pairs that override the current ones.
Update:
The scope is in fact bigger than previously thought: 2 other options were forgotten that need to be set only in a Unity 2D session:
/apps/metacity/ general/ show_maximized_ titlebars false general/ auto_maximize_ windows true
/apps/metacity/
A new simpler, more generic solution was thought by Didier: adding a command line option to metacity where one could pass a file containing a set of GConf key/value pairs that override the current ones.