IMHO, I didn't think the original Mac ROM patching scheme was bad: vectoring all the Toolbox routines via RAM addresses isn't so dissimilar to how the BBC micro (and I believe the Archimedes) vectored all the main OS routines. Given the number of bugs in the 64kB, it made good sense ;-) . The problem is when they started to rely on specific ROM addresses for subroutines in the patches ( I guess, which is part of this topic).It's not great, but the thing is by that point, they were already committed to this course. To a certain extent, that's why it must have been very obvious that "classic" MacOS's fate was sealed by System 7, and why 8 was meant to be a redesign. The ROM + patch idea, the way it was done by Apple, is a huge design defect in the system. It's interesting to compare this to how RISC OS does it with modules that are (mostly) soft-loadable over the ROM without needing to rely on the details of how the ROM is organised. Not that RISC OS aged much better than MacOS, but in this case, the design is clearly better.