you would of course still have to complete a sim course to get to grips with the particular airline SOPs
One of the principal ideas behind the MPL is that that all the type-specific training is undertaken to a particular airline's SOPs. This, of course, means that the airline has to be involved in the student's training. At the moment, in the UK, no airline appears to be prepared to make that level of commitment.
My understanding of the original concept behind the MPL as that you cannot undertake one on your own - you have to be supported by an airline. Of course, now the MPL is a reality no doubt certain "requirements" will quietly disappear.