@The-Profit I am sure that the arduino library and the MySensors library are different in how they talk to devices. The MySensors gateway is not only supported as a serial gateway, though I think that is the most common way that people connect. MySensors also supports an RS485 wired gateway, MQTT gateway, and a few others. Check out the "Selecting a gateway" page for more on the gateways. If you have MQTT already set up for HomeSeer, you may not need any gateay at all (could be wrong on that though), not exactly sure as I have never used MQTT.
As @Tmaster mentions, you could build a dimmer sensor, but if you are going to do that, you will want to make sure you make one that is safe for inductive loads. If you don't have one for inductive loads, you could easily burn out the circuit.
I have not had the time to dig into this one again, though I hope to soon. I have my hands full at the moment with my weather station node that I have been building. Once I get more done on this, I will post to this topic again.