Wow, this thread took off while I wasn't looking! )
The online rebuild is currently specified in a PL/SQL procedure
which is part of the Site Wide Search package. It is now in an
"alter index" statement; it used to be part of a "create index"
statement in 3.x.
I think all you need to do is remove the word "online"
(search-tables.sql) and add a comment telling the user to put it
back if they have EE.
Oh, and make sure that some mention is made of all these
comments in the installation docs, and perhaps use an
identifying string in each one that people can grep for.