I've restarted another game in WEGO mode that time. Because of heavy looses and 6 strikes (d'oh ! So many strikes coming in one turn, is that normal ?) my NW has dramaticaly decreased and there are mutinies in my army.
The problem is that it causes looses in my artillery brigades, that cannot be reinforced, so that after 2 turns of mutiny I have lost all my artilleries (and I guess the problem would be the same with any other support unit as tanks or assault troops).