The main danger, of course, is that BJP reacts to this by provoking communal violence in order to cause Hindu consolidation against the minorities: it may well be their best (politically) bet at this point.
Ag, you seem to understand Indian politics and yet you ignore your own wisdom when making posts about religious riots. It is just irrational behavior on your part. You made the correct point that when the election becomes about the BJP or secular forces vs non-secular forces, the secular side will win every single time. So what incentive does the BJP have to create that paradigm themselves? The BJP has all the incentive in the world to keep their opposition divided among multiple parties. That will not happen if they start religious riots and try to divide India.
Also, the sort of consolidation of the non-BJP vote you saw in Delhi will likely not occur in rural India where caste politics is still king. So all the BJP has to do is make sure they keep their base (which they can do without riots) and get enough of the secular middle class vote in order to win. Remember, the lower class vote will likely swing against the incumbents.
Furthermore, AAP and Kejriwal are much greater threats to the BJP than Congress. As this election shows, people are still tired of Congress and Kejriwal represents one of the only viable choices to defeat Modi in 2019. The issue for AAP is gaining support in the rest of India, not just Delhi. Divisive riots would only be a catalyst for that.