Ok, Heathrow's runways are 1415m(ish) apart. Does not allow for simultaneous independent approaches in IMC therefore they are dependent on each other, unless VMC. 9643 and other ICAO docs stipulate you need at least 1500m for independent arrival streams, so in theory 5km airport would allow this for 3 runways.
CATIIIC approaches would still get you a landing clearance at 1nm if approved by the CAA and you are warned. Nothing wrong with that.
As to time based departures look at CAP493 Section 1 Chapter 3 Page 9. Certainly has 2 min separation there and more.
ARETS= Around The End Taxiways, best way of reducing runway crossings.
Gonzo is usually on the mark with this stuff.
