I agree with Raymond.  It would be strange to have the API that is obviously designed to pre-compile the regex not pre-compile the regex.

If the concern is that a non-precompiled regex might get bumped out of the cache but you want a way to only compile a "bunch of stuff" on demand, then the thing to do would be to make a proposal for a new API that does that, and we'll discuss the merits :)

It seems to me that contexts that care about startup time can use the deferred compile API, whether the new (it it is accepted) or existing one.  If an application cares about startup time and is using re.compile at startup, then that is an application performance bug.