Although I am in for 14 cars, if an alternative route is needed I would support a base 7 car set of DTS + TRSB + TBF + M +TBF + TRSB + DTS. with a pre-order option for 3 car add-ons of TU + TF + TS, and an unpowered M. A 4 axle M power car with traction tyres should be able to cope with a full 14 car set which has 16 trailer bogies - fewer than my 2 + 14 Eurostar set which has 2 motored and 18 trailer bogies, and manages 2% gradients and carefully laid 9 inch curves too, on my layout. I can certainly manage with basic interiors, no tilt, and no fancy nose set-up. Tinted glazing can conceal a lot.