I found this PG59IMG.zip that is a leaked version of the 1.55.531.3 OTA as a full, fresh install to play with earlier:
From Leaked ROM 1.55.531.3 / Radio 11.59.3504.00_11.16.3504.20_2:
To find, go to the page, thank football, and look under Generic Releases
Click that link and you will find it.
This is the same as using our return to retail stock PG59IMG.zip file.
yogi2010 has already successfully flashed it and reported that the HTC unlock tool works on this version.
Now we just have to figure out how to get it to install for people already on the update - i'm gonna go make dinner and see my lady for a bit - but - when I get back that's what i'll jump on - it leads to the S-ON to S-OFF issue anyways because if we can get this to flash for people on it currently then we are one step closer to effecting a downgrade-to-S-OFF option.