An on-demand water heater is perfect for this
The key is to regulate the rate-of-flow down quite low, so you can get sufficient temperature rise without having to use a gigantic water heater.
Regardless, this is like trying to air-condition a gazebo. The dishwasher itself - box, pumps and racks - has a lot of thermal mass, to say nothing of the dishes! Preheating the water to 150F will do precious little when it equalizes with all that other thermal mass. (Remember the water volume in a dishwasher is not high; it doesn't fill with water like a washing machine). It really depends on the dishwasher's internal heater, which needs either high current, or time.