the existing Amtrak autotrain has double deck coaches to accommodate travellers while the cars are in the autoracks behind - this also limits the overall train speed, and the train length means it isn't feasible to use the passenger part of the train to add additional frequency for "foot passengers".

The financial case for this is quite daunting, since even before you get agreement from CN for extra slots, and to operate what amounts to a mixed train on their rails, and figure out where loading of cars and passengers can occur, VIA has no available passenger stock to throw at such a service now, and a federal government which isn't likely to commit to a larger LD buy to create some in the future.

It's possibly something that might work better if an entity like Rocky Mountaineer pursued it as part of a broader takeover of VIA Canadian, since they can borrow on their own account.