Yes I have adjustable shocks but they have been on the car for years without any issues. I does sound like an ABS related issue though and the Lotus computer noted it sensed no sensors at any wheel when we ran the ABS bleed program. The computer did cycle the system though Where is the ABS computer located???
In reading the post you copied in the poster notes the pedal would go hard in this instance which is the opposite of what is happening. I cannot get the pedal hard and where I was perfectly positioned to heel/toe under hard braking I now have to use the side of my driving shoe was my sole is below the gas pedal. This lack of pressure is what caused me to look toward the master cylinder as the cause of the issue...I have one on order.
I read that as 2 related issues...
1)pedal going soft due to excessive temperatures, from the front brakes doing all the stopping, therefore boiling the fluid at the front calipers.
2)rear calipers not working due to ABS DRP problem, causing front brakes to do all the work.
Any "air" meaning gas from boiled fluid, in the system, will make the pedal get soft, even if the rear hydraulic circuit is blocked off by the DRP.
Does the pedal get hard again after bleeding all the fluid? If so then in that case it would not be the master cylinder. (not that the 2005 Elise pedal will ever truly feel hard, they always feel soft compared to what they should feel.)
Or..........
I suppose it could be that your rear calipers/pads are dragging on the rotor all the time, due to the parking brake adjustment for instance, and generating heat, boiling the rear fluid at the piston. That way the rear circuit would be full of air and not able to exert pressure, hence the lack of wear, and also giving the soft pedal. I have seen that on a car with a badly adjusted parking brake cable, the rear fluid boiled in normal street driving in a few miles and turned black.
What is the color of the fluid that comes out of the rear calipers when you bleed? And what is the color of the fluid that comes out of the front?