It will be good, if you will have a good way to stir. In 30 liters I found temperature differences of more than 20°C to be possible, and ones around 5-10°C to be pretty common. So make sure some kind of automatic stir is there, or heat really, really slowly.
Be sure to use system that, if probe is short circuited or missing, switches off heating and preferably causes sound alarm. If possible, use driver that allows for three probes, and place additional ones on exterior of your kettle and on the plate's chassis. Have fire extinguisher nearby, a lot of liquid and long term electricity heating are sparking, fiery kind of friends. Never leave it without someone aware what's happening in alarm's distance.
What I would do would be to heat it to 45°C, stirring, and then just wrap it in all the blankets I have at home. This would keep wort in acceptable temperature for up to 10 hours. Not optimal temp, but acceptable one. Long enough time to sleep or go to work. Then, I would reheat and stir manually, every few hours when I'm at home. Sure, less precise. Sure, more work. But also far less chance for accidental boil, fire, leaving it cold unnoticed and so on.