Kudos to @ckemper for taking time and responding. As I wrote earlier, I am OK with this no-solution-from-kemper-side and I knew it will end up like this. That's why I modded my DIY pedal mechanics and now it works well.
Changes I made:
1. I set up the pot so in the heel position I have start of the pot where there is small margin of 0 resistance, so heel position is covered.
2. As I don't have access to custom 200 degrees turn pots, or specific taper characteristics I have no other choice as to use common 300 degrees turn pot, 10kOhm, linear. So the toe position has to be taken care of mechanically. I removed the switch, which as @Burkhard mentioned, is not really necessary thanks to Bypass@xxx function which works well. I replaced rubber parts with stiff parts, so there is hard-end at toe position, which is covered by 5% margin @timo mentioned earlier.
Only one issue has not been resolved: There is manual re-calibration needed if pedal is disconnected-reconnected from powered-on KPA. As I don't disconnect pedal frequently, I can live with it.