Few points that come to mind on how the politics will play out with Yogi Adityanath in UP:
1. Yogi will keep the media obsessed for next two years which means a disproportional attention to everything he does. Think Gujarat from 2002 - I am a great believer that the obsession of media with modi and attacks on him made him a bigger leader. Because even the smallest positive action taken by him got more attention that it would have gotten otherwise. Same will happen with Yogi. And that leads to further consolidation of party's hindutva support base. And to certain extent, it helps with the class consolidation that Modi has been trying his hand at, as evident from demonetization. Cant blame Modi to play that game. 2019 will be practically Modi Vs entire opposition consolidated. He would be stupid to not consolidate his own support to tip beyond that important 50% mark.
2. Yogi will actually be stronger on law and order, and corruption. You can call him communal all you want, but his "yogi" (ascetic) image comes with a sort of integrity which appeals to masses. If he can project himself as someone who is working for infrastructure and jobs also, I think he could become a formidable force in UP.
3. Wont call this a masterstroke but wont call it a gamble either. I guess there weren't any safe options for BJP. A Rajnath or a Maurya would have been a status quo, but Yogi presents a unique opportunity for BJP to sell Hindutva in a positive way to the entire nation and demolish the pseudo secularism and divisive politics for good. Lets see which way it swings for BJP.
Of course all this happens only if Yogi Adityanath doesn't commit any blunder and BJP is vigilant in the state for any sort of violence that could be incited to change the narrative against Yogi/BJP.