If I were building a "modern" Clubman...

1) It would be steel - Reynolds 953 stainless steel

1a) Geometry would be relaxed, not aggressive. STA and HTA would be 70° or 71°, and chainstays would be ~440 mm

2) I'd use a Shimano Nexus 8 hub and cantilever brakes front and rear

3) Haven't seen anything like it, but believe it's one of those "everything old is new again" concepts

4) It's all about getting back to basics while exploiting recent advances in technology like eight speed internally geared hubs, lightweight high strength stainless steel tube sets, and lightweight component groups

I'd add that frame geometry should be traditional, with horizontal top tubes and gracefully curved fork blades