I grew up with the Sierras and was a bit sceptical about ST at first. However, in 91-93 it worked well, the racing was exciting and there was plenty of variety by 93. I just think in hindsight the "wings-for-all" rule in 1995 was a disaster as far was the racing concerned.
What I was getting at re: silhouette formula was that in the Group A days mass-market production cars like the Sierras, Rovers, Commodores, BMWs were RWD, so the groundwork was there for a competitive race car by either fitting a turbo (i.e. Sierra) or big V8 (i.e. Rover SD1). The manufacturer could directly link the race car to the road car in marketing (
this being a familiar example) - the actual race car isn't what is being advertised, but the "halo" effect it has on the rest of the range.
Nowadays RWD is much scarcer in production cars, and a 400/500bhp FWD car is totally impractical. So to have a touring car championship with spectacular cars (let's say 350bhp+) and more than 1 manufacturer involved, silhouette is the most cost-effective route. Sticking to something production based involved hideously expensive RWD conversion.