Edit: Ignore this, check out my next comment.
Summary
I doubt it will work. The command to switch between the extended ( M1025 M1) and regular (M1025 M0) Z axis is just setting a 0 or 1. If the commands included 221 and 125 respectively, then it would indicate that they had made the firmware somewhat flexible. By being on/off, it tells me that they hardcoded those lengths in the firmware for the Z axis.
The firmware is available for the original. I haven’t heard of anybody that’s attempted to modify it though. The firmware for the v2 took some effort from the community to learn how to build and package (search the forums if you’re interested). As far as I know, nobody has taken the time to do that for the original. I suspect that a lot of the v2 work would be applicable to the original, so it should be easier going. I’m interested, but I don’t have the equipment I would need to recover from any mistakes. So it’s not something that I’m willing to try. And I don’t have an extended Z axis that I want to repurpose as an extended Y axis 
Is there a reason you can’t rotate the object and print the long axis vertically? I’ve only made a few models that need to be printed in a certain orientation (for shear strength). The vast majority would’ve just required some extra supports to print rotated.