After reading about the critical extension startup order for CUPS, it occured to me
that the following change to startup script processing would not be too difficult.
1. After each file in /usr/local/tce.installed is processed, it is moved to /usr/local/tce.installed/processed.
2. An extension with a load order dependency could call a function which would process the prerequisite
startup script ( if it exists ), and move it to processed.