I think that you can change grounds to desertion after filing grounds for cruelty if the two years (or is it three?) threshold period passes by while the case goes on on grounds of cruelty and the separation in the meantime exceeds the two years requirement.
Also, one more IMPORTANT point that we husbands often miss: Wife files for DV, 498a, etc. and for divorce on grounds of cruelty. You, the husband, frustrated and angry, just keep defending yourself, may be even get arrested and released on bail, whatever. The worse the nightmare, the better. Why? Well, if you get all these other non-divorce cases thrown out fast, then you can and should file a counter-application for divorce on grounds of cruelty by wife. There are MANY caselaws in support that the filing of false cases tantamount to cruelty by wife. Point is: Yes, you can change, or rather in this case, add the grounds for divorce. And do you know that cruelty by wife disqualifies her from maintenance? I bet most of us are unaware of this.
So... when a wife files a false criminal or quasi-criminal cases, feel happy.. even distribute pedas in front of her and give one to her too! The more she files, the more happier you should be if you keep the end goal in mind.... just keep delaying the divorce proceedings until the criminal cases are disposed of. In fact, you can file your counter-divorce case and ask the Judge for a stay until the criminal cases are disposed of.
I HOPE THAT THIS INFORMATION IS PASSED TO EVERY VICTIM OF FALSE CRIMINAL CASES. MOST FAMILY COURT ADVOCATES TAKE NO STEPS IN THIS DIRECTION BECAUSE THEY ARE MOSTLY IDIOTS SO IT IS BETTER IN FAMILY MATTERS TO DO YOUR OWN READING, GET ADVISE ON FORUMS SUCH AS THIS AND REPRESENT YOURSELF.