TL;DR
1. Add signal support to thrusters to read fuel amount and oxidizer amount (similar to monitoring two storage tanks as that is what the underlying implementation seems to be).2. Add a signal to the platform hub to enable specific determination of thrust paused/automatic state. I note that the underlying SDK API reports many more states, some of which may also be useful. Those state returned as an int signal would be fine too.
What?
In order to precisely control fuel flow you need to control how much fuel is in the tanks or specifically the flow rate while thrust in on and suspend flow when it is paused. When a ship is in thrust paused state there is no current way to immediately detect this, thus is is not possible to suspend delivery of fuel. The end result in the tanks will fill, and when thrust is re-enabled, the ship will apply full thrust until the fuel is used up and the actual delivery flow can have its impact.Why?
If a ship is paused and is restarted say in the outer system routes, then there may be a high chance that a fast ship running at reduced flow will be destroyed as there can be no limiting of thrust until the fuel level drop lows enough on its own.From the discord, I get the impression there are many people trying a variety of method to control the speed and/or fuel efficiency of their platforms via circuits. A considerable part of the design challenge in factorio is circuits and adding full signal monitoring and control to thrusters and more complete monitoring adds to the mechanisms available for more advanced players to engage with as well as the possibility of more satisfying results of one's platform designs.