The probe is not waterproof so you will need to come up with some type of thermowell for it. I just used this type of setup to run an e-BIAB test batch two nights ago. I snaked the probe into the mash through my barbed fitting on the lid and put it in thermoplastic tubing with a brass butt end barbed fitting on the other end. It worked well and kept temps within 2+/- degrees once it ramped up. I recirculated the mash and it only had to kick on a few times during the hour. It can handle a 1500 watt element just fine, but you have to change the jumpers inside to handle heat vs cooling.
That all being said, a PID controlled RIMS or HERMS is really the way to go for an end game solution. A PID can turn on and off in split seconds. The Johnson only cycles on and off with a 2 degree swing, even set at its narrowest offset setting.