The question is very simple.

The can not read directly the "params.ini" files or it they want to do it, ask them to check if MULTISITES_ID is present and in this cans read the "params_".MUTLISITES.".ini' file.

They have hardcoded the reading of the "params.ini" files.

Perhaps they also did other things during the install. I don't remember.

The problem is that Gantry is like a library that is included in each RocketThemes templates and that need to be fixed each times. So the only place where the fix can be done is in the library that Rocketthemes includes in their distribution and not after the installation that would require to create patches for each templates as Gantry is replicated as many times as there are templates.