(For the benefit of anyone else) Jan and I just had a short phone conversation where we realized that we didn't actually disagree on anything other than where to draw the line between "design" and "implementation".
The current boot archive design/implementation has fragile spots with respect to state & config files (such as path_to_inst and devid_cache) which are present in the archive but are also subject to automatic updates at essentially arbitrary times while the system is running. Jan & crew are working on fixing these. - Bill