Upon further reflection here are some thoughts. I think this pod arrangement is workable. I think all the points about tapered sides etc. are mostly red herrings. What matters is the "waist level" width, which makes the current configuration work. It will allow this configuration to work too.Also in a straight single level car there can be much more baggage space since Coach like luggage racks can be kept in place, perhaps even done in the airline Sky Cabin type configuration, making the space look more open.
So if we simply look at the 12 Roomette space (the proportions remain the same if an entire car is filled with pods rather than just the current 12 modules), with the Roomette arrangement you get 24 berths, and with the pod arrangement we get 18 berths. Hence on an average a pod fare will be higher than a per berth fare in Roomettes.
The good thing is that single travelers will get a cheaper lie flat berth. The bad news is, if the proportion of people traveling is skewed towards two travelers together rather than singles, there will be some loss of revenue. But that may be manageable.
The issue of the hardware cost still remains a very potent one, as is the cost of maintaining the more complex electrical and electronics of the seat deployment mechanism. Considering how often I find glitches in the fancy airline seats in operation I think that will be a significant consideration, no matter how much we may wish to wish it away.
Now consider this. If this were to be applied to an NJT style multilevel car using only the upper and lower levels, leaving the mid level for baggage space, toilets and perhaps Handicapped space(s), with a little finagling with dimensions, I think it will be possible to fit 12 modules per level, i.e. a total of 36 pods (+ one handicapped space at the mid level). Now things start looking interesting. Of course overhead baggage racks disappear which means there has to be significant floor mounted baggage rack space at the mid-level, and the thing will appear more cramped than the open single level. This is almost always the case with bi-levels anyway. They just are more cramped because less space is available to play with. But 36 seats makes it possible to sell a seat for slightly less than double the Coach fare. That was the attraction of the Slumbercoach configuration too.
But then again, in a single level car, old fashioned sections will always trump any of these other arrangements in terms of capacity and comfort, though at the cost of not really having full freedom of what configuration you switch your seat to be in at any time of the day. Which is the one thing that motivates exploring possibilities with modern pod cabins.
If you really want to stuff as many people as possible with lie flat space and more or less shared seating, there is nothing to beat the standard Indian Railways AC 3 Tier Sleepers. But who wants to go that far?
Note: Photo Credit:
http://www.trainman.in