Yes - and I did it for three tanks. It appeared to work on test, but was never installed because there was no need - the meter didn’t have a ratchet and was not replaced by the time the friend I built it for sold up and left! (It was a big 5-bedroom farmhouse B&B.)
It used an emonTx V2 (yes, that long ago) with a customised version of Robin’s sketch. One tank had priority, the other two were linked to each other by pipework but all had their own immersion heater and 'stat. The algorithm was: the priority tank turned on at a low “energy bucket” level in burst mode, when that failed to empty the energy bucket, it was followed by one of the other two chosen alternately (so as to share the heat). If that didn’t empty the bucket, it got exported. The main changes were just adding extra setpoints to turn the triacs on and off at carefully chosen levels - plus the logic to select the two linked tanks alternately. The power switch was a large cast metal box with three triacs bolted to it, using the box as the heat sink.
Robin has a sketch for multiple wired loads on his website - mk2pvrouter.co.uk