The MPL wil never be a replacement for the conventional route to an ATPL, via CPL/IR. It is likely that the MPL route will be at least as expensive as a modular ATPL and will enable you only to sit in the RHS of a specific multi-pilot aeroplane type (e.g. if you do the MPL on a 737 it will not be valid on any other type or class of aeroplane without considerable extra training).
It is notable that enthusiasm for the MPL among the airlines (except KLM, who started it all) has waned considerably over the last two years and it now looks as if few will take it up. This is significant as entrants to a MPL course must be 'sponsored' by an airline. (In this case 'sponsored' does not imply that the airline will make any financial commitment or guarantee of employment).