CDU/CSU-FDP-Greens probably is the best option but if red-red-green means Merkel will be replaced by an actual conservative (FLAWLESS BEAUTIFUL JENS SPAHN) who will win in 2021 I'm all for it.
Considering that Merkel is a conservative, and bar one issue, one of the most right-wing economically and conservative in Europe, I really fail to understand the concept that Merkel isn't a conservative.
While she did force extreme austerity on countries like Greece (and I probably agree with you on the fact that it was too extreme) her record in Germany isn't that right-wing. She is regarded as one of the more moderate CDU politicians.