Some quick back of the envelope calculations....
A Venture car, after taking out space for crumple zones, ADA restroom and ancillary closets and stuff has about 750inches of length available for passenger occupancy.
If each Pod takes around 70-72" as is true of the Delta Pods, you can have about 10 rows of those in 750" with a couple of feet to spare.
A typical Delta Pod is about 40" or so wide. So at most you can have a 1x1 layout in a cabin that is 120" wide if you wish to have an aisle.
Which means you can have 20 such seats and that is the absolute maximum capacity.
Compare this with a Viewliner Roomette like layout. Each Roomette has a footprint allowing 9x2 in the same space. It has a maximum capacity of 18x2 = 36. Admittedly some are sold as singles, but at somewhat elevated fare. But still it is not clear to me how this pod based car would have a lower fare than a Roomette based car.
It is also worth noting that any further space that is lost for ADA accommodation would be the same in either configuration losing equivalent amount of seating space, except that for each row lost Roomettes lose 4 berths whereas pods lose 2 seats. But still I do';t see how Pods will be cheaper fare than Roomettes.
Doing a Herringbone arrangement may allow addition of one or two more rows while keeping enough width for an aisle but that still does not quite get us there.
There is a reason that Slumbercoaches were built, which takes advantage of vertical staggering thus allowing more capacity and that is what allowed the lower fares in Slumbercoaches.
We already did this exercise somewhere. The 350 cabin is 18' 5" wide and has eight across Delta One Suites:
https://aircraft.airbus.com › a350-clean-sheet-clean-start
Dimensions ; Overall length, 73.79 m ; Cabin length, 58.03 m ; Fuselage width,
5.96 m ; Max cabin width, 5.61 m ; Wing span (geometric), 64.75 m.
Max cabin width: 18 ft 5 in
Cabin length: 190 ft 5 in
Fuselage width: 19 ft 7 in

Overall length: 242 ft 1 in
So it was pretty easy to just cut the airplane fuselage in half and figure out that a train could easily hold four sets and an aisle with 9' 3" needed to do so.
Note that the seat diagram is a bit misleading. The seats do nest together more and when laying flat they are side-by-side although staggered.