You might try posting in the Homemade and Modified section to get the attention of some modders.
I believe the low mode uses a resistor that could possibly be changed to match the high mode. I'm not sure how it actually works, but my understanding is that the difference between the single stage E2DL and the Hi/Lo version is that the single brightness one did not have a different resistor for low, so it was technically a Hi/Hi, giving the same brightness(where a tap would have changed it on the dual mode version).
I will try to find a link to where I read that.
edit: another option, and one that I would like for allowing the use of rechargeables, would be having the converter changed to a Downboy for use with 2xR123, or a GD for use with a 17670.