I speculate that the dramatic change in the context of Yun Zhong Ge is caused by the strict policies of SARFT again. SARFT has become so inflexible and unnecessarily stringent lately. First, they are still giving Da Mo Yao an extremely difficult time and has not approved the permit for national broadcast. Now, I think Yu Zheng is shrewdly circumventing this political obstacle by asking his scriptwriter to remove all historical references in the original story to avoid any conflicts with SARFT. The scriptwriter for Yun Zhong Ge also wrote the screenplay for In Love With Power/Beauties Without Tears.
In terms of the cast, only Chen Xiao has been announced by Yu Zheng to play Liu Fuling. I heard the production team has not made a final casting decision for Yun Ge yet. Yu Zheng previously disclosed that he would offer the role of Yun Ge to Zhao Liying if Female Prime Minister has high ratings. Unfortunately, the release date of Female Prime Minister got postponed.
There is still no official news about casting decision of Meng Jue. I originally felt Yu Zheng wanted to cast Han Dong as Meng Jue. But for some odd reasons, I don't sense that intention anymore. There are also wild rumors on weibo that Yu Zheng wants Wallace Huo to play Meng Jue. However, we should just take that info as speculative news and not anything substantive.
Personally, I'm not a big fan of Yun Zhong Ge. I have a feeling the female protagonist will drive me insane and get on my nerves, so I never even bother to read the novel. I read a detailed analysis of the story instead and spent some time on the Yun Zhong Ge forum reading reviews. My interest in the TV adaptation only increased after I heard that Yu Zheng would reunite Chen Xiao and Zhao Liying in this production. But sadly for me, this fact has become wishful thinking because we still don't know who will be cast as Yun Ge!
I am also not too bother by the changes in the historical backdrop. In fact, I'm actually looking forward to it! LOL. I like the idea of a wuxia setting. I've been bombarded with too many historical twists in the Chinese drama world lately that I want to see something refreshing. If the scriptwriter can improve the flaws of the original story and the production team can entertain my eyes with beautiful costumes/sets and well-choreographed fight scenes, I don't mind these changes.