Everyone's made some good points as to why openacs developers wouldn't want to inline queries. And Jeff's point about the parser being difficult to implement is well-taken.
For my current effort, OTOH, minimizing startup time is of huge benefit. I spent 15 minutes and implemented OACS_FULLQUERIES as a persistent array (see http://mini.net/tcl/3469 ), and just made db_qd_load_query_file a no-op. This benefited startup time enormously, as you'd expect, and my work now proceeds faster. OpenACS' implementation of OACS_FULLQUERIES is different than my/nstcl's own, but using a trace in this way would probably achieve the desired results.
Anyway, although I can see why it's not appropriate for the toolkit, I have only worked on single-db projects to date and I still like the idea of inlining. I might revisit it someday by porting my ugly perl script to a tcl one that uses ParseTools ( http://www.oche.de/~akupries/soft/ptools/ ). If it worked as advertised, it might actually do the trick.