The correct naming is thermostat.
The FZS600 has 2 switches. The first for switching the fan, the second for switching the warning light (at a higher temperature).
The FZS1000 only has a single sensor. Switching and warning is done by the electronics inside the cluster.
The multi-gauge is this:
Some discussion about it is ongoing here:
http://foc-u.co.uk/index.php/topic,13218.0.htmlIt is able to read the sensor and display the temperature. You only need to get any sensor into the cooling system.
By looking to the pictures I guess it is not possible to use the FZS1000 thermostat directly, routing of the hoses is different.
Maybe you manage to replace the warning light switch by the FZS1000 sensor.
Next option would be to insert the above mentioned adapter (from Louis) into one of the hoses.