Hey Zooker
That's great, but same would apply at OVC at 300ft...arrival still wouldn't be visually acquired until around 1nm from touchdown (assuming standard 3 degree glide, and good visibility)....departure would disappear shortly after take-off...so still less than standard separation.
In order to do this as Chevron pointed out there must be a 'deemed' separation between arrivals & departures? If so, is this a local separation standard? (I.e. MATS 2...and based on a local risk assessment?)