Following the lead of Grand Ayatollah al-Sistani and Moqtada al-Sadr, Abdul-Aziz al-Hakim, head of the Badr Organization, has now voiced his opposition to the US SOFA. This means that every major Shia faction in the country is now openly opposed to the US proposal.
The USA wanted up at least 13 permanent military bases in Iraq and it demanded that US citizens be granted immunity from legal prosecution. It will have to do with just (barely) controlling the Green Zone. As for US citizen, whether uniformed soldiers are mercenaries, they will get no special status other that of unwelcome invader.
The occupation forces and the Shias are now on an open collision course.