Leave overrun fuel cut off but setup a gp rpm limit as shown here, it should act pretty much the same as the overrun fuel cut shown but won't cut when CAN DI 1 is active.
Not to take anything away from you post, I love to see these ideas coming through - but Im just mentioning this in case you werent already aware of the "quick trim" function that has been around since the G4, it will do this same basic calculation and apply the result to the fuel table for you (you still need to manually type in the measured value though). If you have a log open and the fuel map on the same page, click on the cell in the fuel map that you want to adjust, then hit the M key, it will grab the target lambda from the lambda target table, you enter the measured lambda from the log and it will apply the correction to that cell for you.
The normal error high setting is 4.95V and error low 0.05V for a temp sensor, suggest you use these to allow the widest operating range while retaining fault detection.
