I'm not sure if you have in mind re=using your hardware with new MySensors based firmware, or if you want to keep your existing RF network and just add a gateway between that and the Veralite/MySensors network. I'm guessing the former, from your questions about arduino compatibility.
Board compatibility should be good. You may need to change some pin numbers in the MySensors libraries and/or example sketches to match your jeenode and moteino pinouts.
A bigger question is the radio interface. Originally the MySensors library and sensors were designed for the nRF24L01+, but there is an ongoing sub-project to add RadioHead support, including support for the RFM69 - I'm not sure about the RFM12B but you can check.
If your RF network is working well, and if you run into any large trouble porting the MySensors system to your hardware (radios), you could also consider creating some kind of bridge or gateway - perhaps MQTT based. An all-MySensors solution (described above) would have some advantages tho.
