dynamics and direction for vocal staves?

Placement of diacritical markings is always for visual convenience - if players cannot see things and understand them, they certainly are not going to play your music correctly. What is most important is consistency. If your vocal piece has most of the space under the staff filled with text lines, then of course you would put your diacriticals above the staff. If you wish to place them below, to conform perhaps to the piano accompaniment or other instrumental parts, then you can always DROP your lyrics lines down a few points. All musical orthography texts that purport to have all the answers are basing this on common practice from existing compositions - *new* music demands new approaches. I wold advise you to look at those editions that are respected for thier clear pages - Henle, Barenreiter, even Dover - and learn from them. Then look at some horrible editions - Southern, International, Musicus - and you will see what I mean.