I've thought a little bit about the communication coming back from the controller (SmartThings hub) and I don't really need orchestration right now coming back from the controller for a couple reasons. The biggest reason is that the light switches and things I have taking action based on some other sensor (motion turning a light on for example) are all off the shelf switches that don't come through my MySensors gateway they communicate directly with the SmartThings hub. I had bought these before I discovered MySensors and started building my own devices. However, I have plans for other nodes that will need to take action rather than just report data so I'll need to solve it eventually.
There are a couple of solutions that would work in this instance though. One, is to make the SmartThings gateway transport work for arduino and/or esp8266 (or esp32). I did it on the Raspberry Pi because that's what I wanted to run as my gateway. However, making the transport work on the other hardware platforms would allow for the usage of the standard ethernet libraries and I know that works for bi-directional communication over http because I've done it before on a MySensors node and that's fairly straightforward.
The second thought if staying with the Raspberry Pi gateway would be to have a node (arduino or esp8266) that is dedicated to receiving http requests and just passing those along to the gateway which in turn could process the message and pass it along to nodes like a light switch, actuator, etc. This would introduce some latency although for me this wouldn't really be a concern because it would be milliseconds and for my use this doesn't matter. It increases complexity slightly as it's adding another hop and therefore another point of potential failure. Again, probably a minor concern but worth noting. The advantage is that it works with the standard ethernet libraries and is well documented and I've got experience doing this so it would be a 'quick win'.
The other option would be to dig into the Linux versions of the MySensors custom ethernet libraries and change / extend those to make the webserver http communications work. Don't really want to do that though.
For me at least the easiest, quickest option is probably the second to stand up a node dedicated to receiving http requests. With probably moving more towards the first solution as time allows and moving off the Raspberry Pi as my gateway and going back to an esp8266 or the newer esp32. That would mean modifying the gateway transport I created, which is fine, and putting the code in there to allow for that. I was using an esp8266 before and I moved to the Raspberry Pi because I had one and this seemed like a good use for it. I had problems at times with the esp8266 hanging and then it had to be restarted which was kind of a pain, so I moved to the RPi. My guess was that it wasn't timing out/closing connections from clients and I could probably fix that.
Just some thoughts on the topic if anyone is looking at how to get orchestration back from the SmartThings hub. It's very doable though and really not too difficult for either option and probably other ways than what I've mentioned. Other thoughts are absolutely welcome on the subject.