for the 4 door car, how about making rear row seats face backward to get more of the vertical heavier part of the human body's vertical weight when sitting (imagine a blueprint from the side of the car) sitting in the middle for a more mid engine feeling steering feel when2nd row is occupied. the Konigsegg Regera also has this really nice arrow looking(looking from above, birds eye view) seating position that gives a narrower front end which can help with aerodynamics and it gives front row drivers a more center of the car visual perspective, which especially cool for the driver. smaller cabin space also means teh A/C or heater heats and cools faster b/c there less cabin air space to heat/cool, so a smaller A/C heater system can be used to save weight and energy needed to heat teh passenger and their cabin space. Smaller cabin space also means less mass needed to house the space, cutting car weight and maybe helping aerodynamics. also, if the trunk space is not fully being used, it can be open for more leg space to stretch out on long drives or just lay back, while the car size and mass is less compared to teh same amount of leg space in a more normal setup where back seats are forward facing and legs cant stretch into the often not fully used trunk space. This would also allow for a more 2 seater car look despite being 4 seater. and maybe its safer for rear seating people too in event of foward end crash? (search Why Kids Should Stay Longer in Rear-Facing Car Seats consumerreports.org) and for a back end crash the the front row occupants would have the same advantage.
you can tell me something if u want at Discord my account called "frankus indian reincarnation" #0328.
https://www.aptera.us/forum/aptera-design-discussion/increasing-average-efficiencies-by-rental-of-usually-uneeded-things r these systems can also exist in passenger trailer system with even 2 seater car explained under "TRAILERS"
car can also be shorter if the vertical trunk space is utilized uses racks that slide and compress on rails, and the racks can be nets so they are compactable, and the hard racks should have nets on them to keep thing held in place when moving around when driving etc. there can be a grid system in the rack so u can pin down objects with pin down plastic locks in the net and holes in the racks, so the racks sort of look like hollow grid: the circles are the plastic pin down locks can can be clicked in or screwed in with a single rotation of hand or as clip hooks, the dotted lines are the parameter of the net which are holding down the object being stored (the 3d rectangle). even with not tie downs the racks are utilize vertical storage by not requiring stacking objects ex. u would want to stack cardboard eggs cartons on top of other things where eggs can slide around and break, but u also dont want to store those cardboard eggs cartons under too much weight so they dont break, the rack is a flat space to sit on above the other stored stuff and the net tiedown can easily keep objects in place from sliding around., flying into the driver passenger space, etc
this can be used to tie things down to surface area of seats to use passenger space as storage space when theres no need for passenger space,
this can be used to utilize passenger space too when theres no passenger, the rack would sit its weight on connections to the dashboard and some solid structure at the sides of the seat.
of course this can also be used in roof rack