Every time I read a letter arguing that the lack of skilled linguists among staff is reason enough not to offer foreign languages at the primary school level in Japan, I wonder if the authors have noticed the polychromatic pachyderm peering over their shoulders as they write.
Skillful use of appropriate material lies at the heart of successful language teaching, and would entirely circumvent the need for high-level language skills among primary school teachers. Even the most cursory glance at the English language section of any decent-sized international bookshop will reveal an extensive collection of children's picture books with CDs, many of which could be exploited very effectively in a once or twice (or more) weekly English story time.
Everybody loves a story, and children would benefit from large volumes of rich and enjoyable comprehensible input that could give them a far greater advantage than either grammar or conversation-based teaching.
The no-suitable-staff refrain reflects the gross national misapprehension among JTEs and native English "teachers" alike that teaching conversation somehow leads to communicative competence. It is this that continues to inhibit foreign language progress at all levels of the Japanese education system.