So, you can, but it will take making a second Midi multi-instrument
in Logic's environment.
Well no, because ultimately you have to cable everything back to one instrument, at which point, MIDI channel 2 from Multi 1 and MIDI channel 2 (18) from Multi 2 will just look like MIDI Channel 2 data.
Like I say, any device that caters for more than 16 channels has extra interfaces for it. My XV5080 has two independent MIDI inputs for 16x2 channels.
But plugins, at least in Logic, only have one MIDI stream coming into them, so you can only use a maximum of 16 MIDI channels at one time.
So, you are restricted AFAIK without reading their manual to 16 channels per instrument - if you want 64 channels, you should do it by using four instances of the plugin.