How hard or impractical would this non-ecomod be on an Insight?
 

I am curious about how hard it would be to add backseats to an Insight. I am not sure if this has been done before, but I'd maybe expect someone who does Uber or something to add backseats to an Insight.

There wouldn't be enough legroom or headroom.

Unless the passengers are the size of a bag of groceries, it would need to be stretched, like this Metro:

https://i.imgur.com/408Tt.jpg

The was built by Dave Cloud, who was famed for another vehicle. He said it wasn't too hard a stretch; but the Insight is aluminum instead of steel. You could probably do a lot with the OEM grade adhesives available today and save a lot of welding.

It seems people avoid welding aluminum, but I don't know why. The kids in my high school group that welded the electric car together with zero prior welding experience managed to get it done with a MIG welder. The sole brake plate (stopping is an afterthought when figuring how to win a race) only broke off once. I advised the driver on the radio to not touch the brake pedal under any circumstance, and to proceed racing as if there was no brakes (which was accurate). I wonder why PGE stopped sponsoring that race series?

I avoid it because my welder can't do it.

You could remove the rear hatch and install a rumble seat!
https://en.wikipedia.org/wiki/Rumble_seat

What if you just gut out the trunk?http://images.gtcarlot.com/pictures/59864144.jpg

I helieve the primary reason to not weld aluminum is the tricky state change to fluid. Get too hot and it turns to a water like fluid and runs all over the place, at least for me. Chill plates help as does flooding with gasses. Great thing about MIG is the area that gets hot is quite small and is flooded with cooling gas.

There's basically no way to do it without rebuilding the car completely. It's not like a CR-Z. It was designed ground up a 2-seater. The foot well is taken up by the gas tank. There are structural braces across that area. The hybrid battery is in that spot. The roof slopes down there. You might as well build a new car.

Uber also bans cars past a certain age, and no first gen insight is newer than ~16 years old at this point.

Besides the legroom and headroom issues, finding a good place to anchor the seatbelts may also prevent the fitment of a rear seat to become suitable to an early Insight.

This is too small for me to read the dimensions[and non-embeddable], but my brass caliper says ~75% headroom in the back.
Exterior Dimensions
A rumble seat could work, or a Gurney bubble; but why not go all the way to a ball turret?

The CRX had backseats in other markets. However, I don't think the Insight has the headroom for anyone larger than a child to sit back there. I'll go sit in mine and see where I'm at though.

The deck you see in the attached picture is only maybe an inch above the sheet aluminum, and the roofline is already sloping significantly at that point.

I stuck a CRX front seat in the back of my other Insight, which is totally gutted right now. The seat is on the floor with no seat rails, and as far forward as possible. The seat won't even let the hatch close. A small bench seat could work for children, or legless and headless adults. Maybe the 60% of a 40/60 split rear seat? This would only work after removing the hybrid system.

Extra passengers could also just lie down in the back!

Where there is the will, there is a way:

http://2.bp.blogspot.com/-zsfOQXUvE5.../s1600/amx.bmp
http://2.bp.blogspot.com/-zsfOQXUvE5.../s1600/amx.bmp

Even if it becomes technically possible, who knows if a modern iteration of the rumble seat won't be faced with a random regulatory backlash?

You should get a civic hatch. Even though my 91 civic doesn't run i swear to god four 6'8" dudes could sit in that thing comfortably lol. It has a lot of room... i guess since it doesn't have any crash protection which takes up a lot of room these days.

Sure this makes a noticeable difference, just notice the size difference between any budget-oriented car from nearly 30 years ago and either their closest modern replacement or some model slotted one class below (yet actually bigger on the outside).

This is true. Cryptinox are you planning on buying a car soon? I see a lot of post from you about rare cars that aren't as economically feasible to find right now. More than likely you need to find an 03-08 Corolla 5 speed. A friend of mine maxed out the odometer on his and still beats on it like its a damn race car (probably has 380k with just brake jobs 12v battery tires oil changes etc...). Much to my surprise that thing takes it no problem and oil consumption is normal. I think right now one of those for $2500 or less without rust and under 200k miles which I think is the way to go. I see them pop up commonly with all of that.
04-09 Prius could be a good choice too. Although ugly and will need a battery rebuild more than likely but the battery rebuild are highly supported since they sold so many priuses. They also can go 300k+ miles no problem with a new battery.
The insight/90's civic 5 speeds are nice just rare now in good condition and the battery in the insight is more costly to mess with.
I think the lack of maintenance required on the Corolla 5 speed will be cheaper in the long run over the couple extra mpg and labor required on the Honda insight.
This is the reason why people love the 4 cylinder Camry's even though the mpg is just average.

I usually see the Corolla as the Japanese replacement for the VW Beetle, as it's known as a reliable and relatively simple car. And just like the Beetle retained some different versions of its engine according to market requirements such as a higher displacement-biased taxation, nowadays the Corolla is still available in some parts of Asia, Africa and Latin America with simpler engines which have already been phased out in Brazil, Europe and United States.