I would also say that band pass filters would be much more interesting than low-pass filters.
On the other hand, if this is a final output mixer, then there would certainly be times when
one would want unfiltered output. With the space between the columns of knobs on the new
version, might there be room for a switch to switch between LP-BP-bypass/off

Or a real dream come true: one 3-position switch for LP-BP-HP, and another 2-position
switch for filter on-off

That would be amazing....

Ernst