Speed limiter

I did my 290 km (180 mi) winter drive yesterday (including 4 QC stops) while trying hard to keep my C-Zero going above 90 km/h (55 mph). In my previous car I'd have the speed limiting function of it's cruise control set to 90 km/h (about 86 km/h actual speed), so driving in the winter with 80 km/h limits was a simple matter of having the accelerator pedal pressed down and letting go when slowing down was needed. With no cruise control and the C-Zero always wanting to go just a little bit faster it has become a chore to try to keep it in both legal and economical limits.

So I wonder, if the vehicle already has a limiter at 130 km/h, could it be changed to 90 km/h? Anyone heard of this being possible?

Even in the summer it's much smarter to just keep around 55 mph to maximize range and you could just keep the pedal floored forever. Trucks, lorries and anything bigger are limited to about 80 km/h (50 mph) around here at all times so they're not a problem either.

Since the battery cares about amps and not speed, one of our hypermiling techniques is just like the fuel economy freaks, which is to output a steady, efficient power level and let speed vary with the terrain (speed up downhill, slow down uphill). This 'constant throttle' technique has been proven to be much more efficient than a traditional cruise control.
Similarly, it is more efficient to coast down a hill if that momentum can carry you up the next hill, rather than regenning down and climbing up (except at terminal downhill velocity, where you're just stirring the wind rather than regenning at a slower speed.))

So, I've been wanting to add feedback for when my go pedal is depressed beyond a certain point, such as a red light that comes on, a buzzer that sounds, or a green light that turns off.
Hacking the car's software has not been claimed by anyone yet, but a standalone circuit should be easy enough. Adding a mechanical switch to the accelerator always poses some risk of the pedal getting stuck, so an optical sensor or magnetic reed switch would seem the way to go.
I've been tempted to add a spring to the pedal that increases load at a certain point in the travel, or a plunger with a notch that makes clicks you can feel with your foot as the pedal is depressed past a certain point, but haven't had the time to pursue this with the requisite level of care.

I contacted the local Citroën dealer and he made an inquiry to service and import. They replied that a speed limit cannot be set. So it seems impossible.

Ideally I'd like to have both - a speed limit and a Wh/km limit, but to stay with the traffic it's not a bad idea to try and maintain a reasonable speed. On Wednesday I would lock my right foot into holding the power meter on the "O" of "ECO" to make my trip, but this meant going as slow as 70 km/h uphill (about 45 mph) on the highway, which can get a little uncomfortable.