I'm convinced that the initial idea of dedicating one Logic Pro Software Instrument for each and every AU3 MIDI channel, can and should be abandoned.
Why?
First, when configured this way, Logic's AU3-committed Software Instruments can't accommodate more than 127 MIDI channels per VEP instance, and Logic itself can't accommodate more than 1000 Software Instruments. Altogether that can impose pretty severe constraints on serious professional work. Will Apple soon open up these built-in limitations? I'm certainly not betting on it.
Second, in Logic, Software Instruments have a relatively heavy computer-resource footprint, compared to the Standard and Multi MIDI Instruments, AND there's no built-in maximum for these MIDI Instruments!
The solution?
As things stand right now, Logic users can catch up and compete with the big-gun Cubase users. For this mission I recommend a new take on the old-school DAW configuration: i.e. using Standard (single channel) and/or Multi-channel MIDI Instruments cabled in the Environment to 16-Channel AU3 port-committed Software Instruments.
The Environment is Logic's mightiest advantage over all other DAWs. No Logic user who already has the brainpower and gumption to compose and midistrate need be too scared to get in there and take advantage of it; this approach does not venture beyond Environment basics. Moreover, a huge advantage of this approach is that it's not necessary to 'hardwire' an entire template permanently; we should be able to change our template configuration without the serious ball-ache of a major template rebuild every time.
Hence I'm working with a "Patchbay" AU3 template in Logic's Environment such that I can readily patch any of my current maximum of 800 MIDI tracks (mostly grouped in 16-channel "kits") to any of 160 AU3 ports, simply by cabling MIDI instruments to the appropriate Sofware Instruments in the Environment.
I've chosen to build into my current template 10 Software Instrument AU3 ports (all 16-channel) per VEP instance; i.e. 2560 potential MIDI channels spanning 16 VEP Instances. But that's just my preference, and my template is not set in concrete. (BTW I'd love to see a decent parametric Tradeoff Study on optimal combinations of MIDI channels vs ports vs Instances.)
I've limited myself to 800 MIDI tracks because I also have to accommodate a very large Environment subsystem dedicated to Orchestral Intonation (which has been using the Patchbay approach for about 10 years though only recently with VEP) and my one and only computer is showing its age (2017 iMac 4.2GHz 7700K i7 4-core 64GB). However, for pro users with a powerful VEP network, I see no reason why a Patchbay AU3 template with, say, 2000 MIDI channels patchable into, say, 300 VEP Ports (4800 potential MIDI channels), shouldn't be feasible. And that's not even close to the upper limits for Logic.