>>1223787It sadly has about 0 chance of happening.
For starters, the shuttle rolling stock is positively massive, iirc it would fit the French high speed lines loading gauge... they would however be completely unable to leave them (and French HSLs will typically end about 20-30 km away from the city centre stations).
So you'd need a terminal somewhere in the fields and a road to drive up to it. Okay, technically feasible but you better have the demand to justify building it (protip: trucks from spain and italy).
But then you run into the bigger problem. You're gonna have to find a way to insert your long distance car/truck carrier in an already busy high speed schedule. Now a pair of 7MW eurotunnel class 9s has no issue bringing the 2,000 tons rakes up to speed (tunnel original safety regs made for an impressively overpowered design), but they're also limited to 160 km/h (so half of what TGVs can do)... good luck getting a slot.
The issue with the drive and walk through design is also that a club or dining car would have to be at the end of the rake, between the locs and loader wagons. Go tell that to the poor sod at the wrong end of the half rake that he's got a 400m* walk ahead of him, during which he'll have to operate about a dozen pressurised doors, and the same return trip to get a coffee. He's probably not gonna bother with that coffee. I guess you could make it work on longer journeys by making access to those car an option you have to book and pay in advance, so that they'll give those cars the closest parking spots.
>*current shuttle compositions are either 2*400m car and coach carriers (cars in duplex wagons; vans, caravans and coaches -including a eurotunnel minibus with a bike carrying trailer for cyclists- in single deck wagons), there's a loader wagon at both ends of each half rake. Truck carrying rakes are similarly split in two half rakes with a club coach coupled right behind the leading locomotive. 
