Not sure if it helps but whilst awaiting the impact assessment progressive capture forms, I've been experimenting with setting up my BPM to 'Wait for Impact Assessment' of which has Urgency and Impact questions (from low to high) - dependent on the answers it calculates the impact which is then used to automatically update the SLA accordingly, e.g. Impact of high and Urgency of high = Priority 1
Seems a very complicated way of doing it, but it works.