Documentation on how to integrate a different controller device

[LupinIII]

Currently the only implemented device "driver" is for a Brötje ISR. Our home has a Elco Thision S / Elco Logon B installed. (side question: the former is the furnace, the latter a control box right beside it; which of the two is the "model" of our system then?) . I have working hardware and can communicate with the controller, which isn't surprising since Brötje and Elco both use the BSB and I wouldn't be here otherwise. But of course there are also some differences. The main one: we have two "Heizkreise", but there are also options that Elco has, that Brötje doesn't and vice versa.

So how would I implement my own driver? I'm not talking about packet sniffing and deciphering telegrams, but rather what I would have to do with bsbgateway specifically to add another device. I've seen that there is a "broetje_isr_plus.py" file, that is then converted to a JSON file. Is the py file necessary at all? It seems on the other hand much more readable than the JSON file, so maybe the "py first, then convert" is the way to go.
Are there any steps necessary (other than changing the "device" in config.py)?
Is there a simple (batch processing) way to query ALL the defined commands and see if the device reacts to them properly?

It would be nice if there were a short documentation (maybe there is already and I missed it?) on that.