Concern: logistics/maintenance and scope creep.

If we do it for this street, then why not this other street, and the street in the next district, etc, and then we will have to do it for the entire Hong Kong. That's not something humanly doable.

My personal rule is to only do it for numbered highways and roads with no/few traffic lights. Those are the kind of roads where an explicitly-stated speed limit is useful. Can't have the calculators wrongly believe they can go 100km/h on a random signal-less road in HK.