The speed limit sign is a constant combinator itself. I may allow to connect some circuit wires to it and then to control speed by means of the received signals.
Could you describe your setup? In what situation you are going to use this?
Like in your picture, as soon as I'd walk onto the concrete in front of the hazard concrete the sign limit would become active or even a stop sign and as soon as i left it would become active again
Yes, being able to dynamically alter the speed would essentially allow it to be a "soft" signal block. This would mean faster trains in high traffic areas! Definitively useful!