Actually, I always get the dialog to rebuild the desktop in OS 8.1 when switching into 8.1 from 7.x. I may or may not have switched from 6.0.8 into 7.x prior to ultimately switching into 8.1. So I can tell you for a fact that switching into 7 as an intermediary stage is not a fix for this problem, unfortunately.

As to hacking the Desktop Manager, if I were a Macintosh programer I would certainly give it a try. But alas, such is beyond my capabilities.