Hello.
It is not possible to connect to REST/SOAP and I really don't find any good reasons for that
What I mean is when you have read about MQTT and when you have tried it then you will find it very easy and simple to use and it makes it easy to connect a lot of different system.
And then you don't want to use anything else
do you mean that you can't see it from mcStudio without network connection?
mcStudio is communicating with mcGateway over your LAN or WLAN.