You are not limited to channels 1-16. You can also can route channels 17-24 or 25-32 to one of the two banks. It is also possible to route individual channels to any of the two AVB streams. Example: EarMix bank 1 (1-8) is routed to channels 1-8, bank 2 (9-16) to channels 10, 15, 18, 19, 20, 24, 31 and 32.
Routing multiple channels to one single stream is not possible ("17,18,19,20,21,22,23, & 24 to input/fader 16"). This is where the flex mixes come into the picture. You would need to use aux 16 (example) to "mix" channels 17-24 and route the AVB send of aux 16 to AVB send 16, if the EarmiX receives AVB streams 1-16. This would mean that you can not "send" input channel 16 in the EarMix, because its AVB stream is used by aux 16.
You should also consider to use a stereo aux mix and include effects (reverb) and/or ambience microphones. Very often a matrix mix is the better option, because it includes all inputs, returns, flex mixes and Main L/R. Subgroups can also be routed to the EarMix.
Possibilities are nearly unlimited... ;-)