I create a simple plugin for my specific use as you suggest
class plgSystemFlexiMultisite extends JPlugin
{
function onAfterRoute()
{
$app =& JFactory::getApplication();
$option = JRequest::getCMD('option');
$view = JRequest::getVar('view', '');
$cid = (int) JRequest::getVar('cid');
$servername=$_SERVER[SERVER_NAME];
if ( $option == 'com_flexicontent' && $view=='category' ) {
switch($servername)
{
case 'mymainsite.fr': $app->setUserState( $option.'.category'.$cid.'.filter_53', '1'); break;
case 'subsite1.mymainsite.fr': $app->setUserState( $option.'.category'.$cid.'.filter_3', '15'); break;
case 'subsite2.mymainsite.fr': $app->setUserState( $option.'.category'.$cid.'.filter_3', '16'); break;
}
}
}
}
Where value '1' is boolean value in field #53 : 'must be also in main site ?'
and 15, 16 are the user id for subsites admins, filter #3 is on field created_by.
It's very easy ... I just created users/groups, one user for each subsite admin.
Subsites contents is all flexi data created by himself
Thanks , powerful and easy
For managing multisite I use seblod but only multisite feature