Abinitio programs are a normal way into the flightdeck of major european carriers for the last 60 years. In most of those programs multicrew concepts were tought from day one. The MPL is just a new name for a reality that has been with us those last 60 years, with varying amount of hours in real aircraft and simulators as they became more sophisticated. For example Lufty has around 5500 pilots, at least 4500 of those went through their own abinitio program, something they did since they restarted their flight ops after the war (which was initially with WW2 trained pilots of course, usual training duration 20 to 25 hours). The last four years or so they ran only the MPL program.
Im with a competitor of Lufty and we started our own MPL program a bit earlier and have flown with those MPL students for the last five years. No problem at all with them, in fact they have usually a much better system knowledge and pretty much the same handling quality as traditionally trained pilots. During their MPL they do the normal JAR FCL PPL SEL and do train a few hours on multi engine piston planes, so they are allowed to fly solo as much as they want to (and their pocket money allows). However they do receive around a 100 hours full flight sim plus around 150 hours FNPT training before they even start their type rating and with that receive a lot more airline specific training in jets before they even come on the line, the training is finished after their type rating and around 150 hours linetraining.