What you can compare AB with ZB is the financial position. In 2003, Air Berlin had a turnover of 863m Euro and a small profit. Monarch have just announced their numbers and had a similar amount of turnover (for the group as a whole).
I can't see why, Monarch couldn't have been the "next" Air Berlin? Their past was very much charter/low cost operations and have diversified into cities and business flights - something which Monarch have tried very recently with flights to Milan, Munich and Rome. Some of which have failed miserably.
I think a theoretical purchase of Jet2 would open Monarch up to a host of routes from the North of England plus another 40ish aircraft, which would double the size of the airline, putting them on an equal footing to TUI.
Obviously the board at Monarch would have no appetite for this considering their 45 aircraft plan from 2021.
Maybe I'm talking rubbish!