"Once you have the ATPL, then you are eligible for a command position."
Actually that's just the first of many steps towards a Command position. An ATPL gives you no automatic right to command.
Suggest you start with this free training:
http://aerosociety.com/Assets/Docs/P..._a_Captain.pdf
An MPL is a Co-Pilot licence with minimal hands on flight training. It can be done with as little as 70h flying and the rest in a SIM.
Post AF447, Colgan accidents, etc the regulators are looking at it again due to the loss of manual flying and airmanship demonstrated by 0 to hero courses.
MPL best avoided or if you really have to then get a back up in place to obtain full CPL/IR in case you loose the job you are after.