Why not?
Oh boy how I can't wait to hear squeaks on the field! Oh wait...I already hear it, and I can hear it for a lot cheaper...at a High School football game.
You say the arrangements will vary, but its going to be the sounds, not the arrangements, and just go ahead and refer to my answer for a little more commentary.
There's a benefit to this? Sure. "Lets bump the number to 200...screw that, 215!" Etc, etc. Yeah, you'll have more people marching, but then you lose the experience of bonding with the whole corps. I don't know about y'all, but 214 names would be a little hard to keep a track of. You sacrifice the brotherhood aspect of corps by bumping the number up for "varied arrangements."
But really, why not? Because you would without a doubt change absolutely nothing other than what instruments you see, and the volume of squeaking on the field. Because you would be increasing corps numbers and losing the bonding experience that IMO is as vital to the activity as the music. But most of all, because in the past, we haven't used woodwinds, and its worked out pretty #### well. I can't think of one show to date that I've said to myself while watching: "Hey, this would sound awesome with some Sax runs in it." Drum Corps won't be the same. Period.
That's why not.
OH! And because you can already experience your fantasy with HS Marching Band. A bunch of schools are adding in synths and amps, and they've already got woodwinds! I'm sure you can get cheaper tickets than you would if you were trying to go to Allentown.