Well, I don't know about your skills in counterpoint.
First, one has to learn to write counterpoint with just two voices and then increase the level.
Not all the instruments have to make different melodic lines, but there is no sense in having so many instruments that play the same. In that case you would add volume and, perhaps, color, but not dramatic interest. In fact, a true counterpoint is very nice but it would add interest that the instruments were self-sufficient, not only going with the voices.
The "vertical" or choral style is good, but for so long is tiring.