As far back as January 2005, the MINI2 rumour mill was generating information about what eventually came to be the MINI Cooper S with John Cooper Works GP kit.
Paul Mullett has since put together this thread, and it makes for interesting reading in hindsight …
… MINI are planning to release a Ltd. Edition MINI Cooper S towards the end of the current, supercharged car’s life cycle … Details are sketchy, but production numbers look set to be limited to around 4,000 cars, which will be very basic in specification (to keep weight down) and will include many unique carbon fibre components to keep the weight of the Cooper S to an absolute minimum … [from this article, the first ever rumour]
… July 2006, the MINI Cooper S with John Cooper Works (JCW) GP Kit will realise the dream with a power output of around 218bhp, a stunning 136bhp per litre, and a weight-drop of 40 kilos. Only 2000 will be built for MINI fans around the globe with approximately 20 per cent staying in the UK … MINI Cooper S with JCW GP Kit will be a two-seater in exclusive colours … [from this article, well worth reading]
And LOADS of other discussion / rumour / etc from long before anything official was known!