I think part of the attraction is not to relate it too closely to individual companies at the moment, as that's what the line societies cover, but to cover the unique challenges of modelling the period. Maybe we should just encourage people to put the company name in the thread title, where appropriate, or to tag it.
The grouping that mainly affects me happened in 1875, when the GWR, Bristol and Exeter, South Devon and Cornwall Railways amalgamated, and the 1923 one was just when the GWR acquired a few extra lines! And there were many other amalgamations and takeovers in the 90 odd years covered.
But a big question is whether it's the place for threads on pre-grouping layouts, for discussing prototype information, and/or for building individual models, finding suitable products and modelling particular period features that many companies used.