If I remember correctly you have 24 months to complete all your ATPL exams, once completed you then have 36 months (from completion of the last exam) to complete your flight training so it might be worthwhile completing all but 1 ATPL exam, so, for example, leave VFR Comm's until then 23rd Month that should give you an extra year.
As for MPL, It restricts your options having to wait for an airline position whereas if you did the ATPL you would have the option of doing some instructing, etc to keep current.