I replaced all of the flutes in my marching bands with pics long before anyone in my area thought of doing it.They were definitely heard... as opposed to the flutes. One year, I was only going to end up with six woodwinds in next year's marching band. I switched them over to various brass, and long after I retired, that band is still "all brass!"...... with the obvious exception of the perc.
Original poster mentioned a marching trumpet. I was a band director for thirty years, and involved in marching bands a whole lot longer than that. I've never heard of a "marching trumpet'"...... unless you're just relegating a normal trumpet specifically to marching band use.