I would beware of narrowing it down to a vocabulary that makes it useful to an even narrower group of enthusiasts than we have today.
Once again, this brings up the issue of "Whom is lojban for?" Personally, I would like to see the involvement of:
1) more non-Europeans (although the response to my proposal to promote it in India suggests that the lojban community is not interested)
2) more psychologists, historians, journalists, accountants, racing drivers, airline pilots, farmers etc
That would suggest that "book" may still be more important than "button" (just an exmaple).