No amount of time in a simulator or dual in an aircraft can show how a person will react in a real emergency when they are the ONLY person there who can save the day. That is why in the major aviation countries - USA and Canada - pilots have to work their way up the aviation food chain and accumulate several thousand hours of experience before they get into the right seat of a Heavy. Those who are unable to handle real as against simulated stress and emergencies will have been weeded out long before this stage.
So, by logical extension, you must log a real emergency to be in any flight crew position on a large jet.
By further extension, that may include those with 200 hrs, and exclude many with 20,000 hrs.
I think you miss the point of what exactly the MPL training is for, and what the intention is in replacing the current CPL/IR method. Bear in mind that many countries have 200 hr crew operating safely under the CPL/IR or old ATPL systems, and have done so for many years.
We should all bear in mind that as individuals, one only ever experiences one type of training, hence I am sure that most are predisposed to argue only for that which they have experienced - open your mind to other arguments.
The debate is, I feel, in the implementation, and not in the concept per se.