Piano accompanying choral groups

As a choral director of a community women's group and participant in a festival of state women's groups (approx 450 singers), I find it difficult to accept the playing style of the piano accompanist. He must be good at jazz improvisation or other improvisation and his technic seems to be adequate. However I prefer to hear the accompaniment of a choral piece played as written by the composer/arranger. My singers appreciate knowing exactly what to listen for at entrances and cut-offs and sing much more confidently with our individual accompanist who, at my insistence, plays what is written, with very few exceptions. I am interested in hearing from other conductors regarding accompanists who never play an accompaniment as written.