I heard a caller looking for a model of car with less pressure required for the gas pedal. Don’t some Mercedes & electric vehicle models have the accelerator pedal operating just a variable resistor? In this case, I’d think changing to a lighter return spring wouldn’t be that troublesome.
Pressure on the gas pedal needs to be at least minimally resistant to prevent accidental acceleration. If there is a problem with long term gas pedal use, learn to use the cruise control; That’s what it is for.
You are correct about the variable resister gas pedal, but lots of cars have that now. The spring is imbedded in the pedal assembly and likely would not be possible/easy to change. Old school carbureted cars had cable or rod actuated throttles and their return springs (usually one and a backup) hanging out within easy reach in the engine compartment. They were very easy to change. In the middle are fuel injected cars with cable throttles and a spring built into the throttle body.
The bottom line is, don’t change it. The spring is that stiff to insure the throttle closes completely when you lift your foot. You DON’T want to experience a stuck throttle, First you say it… Then you do it … so you won’t have clean underwear when the EMT’s arrive. 
I have large feet - US Mens size 16 extra wide. Needless to say, my shoe is about 15" from heel to tip. Which creates a dilemma when selecting a car to accommodate my big stompers. Also, I’m over 6 feet tall, broad shouldered and have long legs. Comfort becomes a REAL issue for me. On many cars, my right knee rests firmly against the center console shifter - which has resulted in accidental shifting-into-reverse during left hand turns. Got rid of that car.
I looked at the Ford Crown Vic, expecting tons of room for the big and tall challenged. But no, this particular year Crown Vic, had an adjustment for pedal-height. Which meant that there was this big honkin motor assembly above the pedals. This caused my feet to be wedged-in down there. The tip of my shoe was firmly in contact with the bottom of the dash if you can visualize. Claustrophobia trigger that was.
Now, since “Evan from Bellingham” was looking for a car with less pedal pressure, I began to wonder if Toyota has ramped up the accelerator pedal pressure ever since there was that “run-away” car thing Toyota had. And Audi had similar claims against them as well. And didn’t Evan say, he tried an Audi too? Hmm…
My point is, just because a car is large, is no guarantee that it’s comfy. Conclusion: I found that a 1994-1996 Honda Accord had the MOST room for my big feet. Those cars have a big cavernous area above the pedals in the footwell for me to lift my feet up and down and maneuver around on long trips. Those small details can make a mountain of difference. I’d focus on some older used cars - Honda too. My opinion is, the more bells and whistles a car has, the less room there is for the occupants.
Here’s my pedal pressure story re: 2001 VW Passat V6 GLX wagon. The pedal pressure was pretty substantial, and it was VERY difficult to accelerate smoothly. It either accelerated too slowly, or the pedal would mash down unexpectedly resulting in stressing the motor mounts. We had to replace them all several times.
Assuming not problem with his left knee he can convert his car to a left foot accelerator. I did so many years ago after surgery on my right leg - it worked great and only took about 15 minutes to get accustomed to.
If run away acceleration from a stuck gas pedal is an issue where the gas pedal drives a potentiometer, an easy solution is to put the pot in series with a normally open solid state relay that gets power (through a zener diode to filter noise) when the brake pedal isn’t being pushed. Then, any application of the brake pedal will cut out the acceleration signal - end of story.
If Evan drove a car for years that had less return pressure on the gas pedal and that worked successfully for him, then I have to believe that this same smaller amount of return pressure would also work successfully for him in a pedal that drives a pot.