sir you already found the solution, there is that spot where the accelerator cable is exposed, mechanics usually pull the cable to rev the engine, we can use a central locking gun with a strong thread/cable. tie one end to the accelerator wire and the other to the gun.
make a timed mechanism or a more intelligent mechanism that keeps the cable pulled until the desired temp is reached.
i was thinking of a way to make cruise control, this might also work for that
make a bracket to fit the gun, design the bracket such that we can alter the distance from the accelerator cable
another idea is to redesign the linkage where the accelerator cable connects and make space to connect another cable for the gun.
if a rich mixture is necessary, then connect another gun to the choke cable.