Whilst WW fly to both CGN & MUC they are not year round or even daily services and you cannot interline with WW at present, although there as been talk of this in the future. The regional service is thrice daily with a very early start 06:00 local departure ouch!
INKJET- even a 0600 start from EMA doesn't give you the chance to get to the office in Germany for the start of the working day because of the clock change - hence many travelling for work will take the last flight of the day the previous evening. As long as you can chose the days you travel WW works well via CGN - particularly with the fast onward train service. I've taken this option when the economy fares from BHX are not than economical and the days I can travel fit.
I agree its only valid in winter as WW do not operate this route in summer but I raised this as bmi are launching the service for the winter timetable.
Departure WW CGN is 1650 compared with BM FRA 1615, both return to EMA arriving 2020.