As stated numerous times before, we need consolidation in markets like Germany.
Without any doubt, there is demand to classic leisure routes from Germany, however in order to make money on those low yield long-haul routes, you have to have a very lean organisation.
Condor trimmed a lot of fat in recent years and became profitable again, however they have a major fleet renewal program ahead of them.
Even Air Berlin lost a lot of weight in recent years, but they were so obese that the threshold to make money with leisure pax is still some major cost saving programs away.
But three airlines plus foreign carriers going for low yield passengers ex Germany to thin leisure destinations is simply too much, so a combined effort might work, but I do not see three airlines independant of each other to markets like TPA, RSW, FLL, LAS not to mention markets in Asia, were the airlines from the Gulf have destroyed fares over the last couple of years.
Using Sun Express, Eurowings or any other relatively cheap labour contract is also neccesary, but again, it is a lot of effort for a relatively low (finacial) return. Further co-operations with tour operators might also decrease costs by a few per mill.