Yes I came across your tutorial (I think this one?) which helped me in figuring out the linking, but once you started with your (seemingly elegant?) code, it went right over my head. 
Maybe I will get there one day, but in the meantime hopefully my post will help my fellow mere mortals and other lower level wizards like myself to get started at least. 
And yes, I found the Rhasspy interface quite nice and full of choices I have only begun to explore… Here is a video I came across (for others, I know you are already familiar):
In particular, there are lots of nice substitution and other options when defining your outgoing JSON structure from Rhasspy. So, now by thinking carefully about this, I will probably end up with only one Rhasspy MQTT Thing, with a number of defined sub keys in JSON to actuate different lights, etc…
I feel I am well on my way to getting the “MQTT to string to rule to command” way working, and will post my working config for posterity when I do.
Thank you for confirming I am moving in the right direction though!