I really don't think we need to up the number of people in the ensembles actually...it is going to get to the point of it being musical, and visual clutter, sort of like many indoor drumine shows. In fact, many shows have become very cluttered recently. All sections - brass, guard, percussion, are now always "yelling" for attention in a way. The idea and contrastof aural and visual space is diminishing
but if I had to choose, I would do marching cymbal lines - not 11 - more like 5, and then spread the other 6 positions out. To me, there is nothing more bad ass thhen a smoking cymbal line
you HAVE to watch the whole thing to see the famous "headchopper" visual they are known for...
but if I had even a 1/1000th of the bad ass that these guys have, I would be happy
from a writing standpoint, more than 5 basses is redundant...4 or 5 are the best situation for writing split parts.
I would possibly add tenors before snares b/c the tenor voice can get lost in the mix
so in short:
add 5 cymbals
add 2 tenors
and add 4 more in the Front Ensemble as needed
my perfect line would be
9 snares
6 tenors
5 basses
5 cymbals
6 marimbas
6 vibes
drum set
2 synth players
1 rack guy