[SOLVED] Control ESP8266 via Iphone hotspot / must also be running fine without wifi

You could, but perhaps not worth all the effort and potential risk (having a stable IOT application without the I).

Now, if you have internet access on site (or even a built in Local Server in a “closed circuit” configuration) … you can do some fully managed setup and data logging. Even full control and monitoring that way… at least when you are in range of the Local Servers AP. A bit more effort, but if you need those functions, then perhaps worth going that way?