PureEngage On-Premises

Is it possible to start a call with com.genesyslab.dtmf.offboard_recognition set to false and after an initial prompt change it to true if needed? 

Most calls to the IVR only need simple DTMF input, but some may choose to use ASR, in which case we need offboard set to true.

I haven't had any luck so far getting the offboard_recognition mode to change mid-call. 

I think, it is possible, but you will have to re-read the VXML parameters again, so it could means that the VXML should be divided to two independent VXML application or use the root application with "some" logic.