FlightPath, I'm a little puzzled about the point you are trying to make - and I'm really not sure that it is going to help the OP (or me) to try and bottom it out.
It is quite true that separation standards are minima and can be increased if a pilot request it or a controller believes it appropriate. So, yes, a 2 minute separation requirement means a minimum of 2 minutes.
However, the separation requirement may originate from a need to establish IFR separation or WT separation. The two are done for different purposes and, generally, it is the more stringent of the two that the controller must achieve. It is important not to confuse the two.
In the absence of a need to establish WT separation, and on a nice day (and assuming that Doc 4444 provisions are applied by the State), ATC could launch two IFR flights within seconds rather than minutes by utilising 'reduced separation in the vicinity of the aerodrome' as Gonzo mentions. When I was operational I did this routinely even with large aircraft. If, however, there was a need for WT separation, then even if the controller can get IFR separation in seconds, the WT separation becomes the limiting factor.
Interestingly, in the UK the term 'spacing' was used with respect to WT requirements in order to distinguish it from IFR 'separation' until a couple of years ago (at which time it aligned with ICAO).