I think London City was a good place to start.
No VFR circuit traffic, London (apparently the best in the world) approach/departures control, one runway, small PPR parking area.
High speed internet circuit between London and Swanwick, satisfying the 1 second video latency requirement.
None of that applies to either Ballina, West Sydney Airport or Hamilton Island, two of which will be Class D CTRs.
I anticipate the Tower Controllers having to be close to the antenna towers, which makes both Ballina and HMI a marginal improvement at best. We already know that West Sydney will be in "centre" close to the airport so once again the savings are confined to building, there do not appear to be staff savings.
We know it works, assuming the standards applied to the cameras, are the same as applied to eyeballs. I only hope that CASA has done it's homework!