Much of this question is more to fully understand MIDI routing and capabilities that are not intuitively obvious. My situation is an obvious misuse of "intended" behavior, but to a critical workflow endpoint. Finding reference material on this is hit-or-miss, and some of the folks here know MIDI better than I ever will.
 
Situation: Geist is the VST of primary focus (VST2). Each engine will fire on discrete channel input, so I have been playing with "Enable MIDI Output" to see how far I can go with this, since internally the step sequencer (pattern banks) and song tab allow for incredibly efficient sandboxing of ideas. Inserting Geist as a simple one MIDI track/one Audio track exposes the majority of things I am interested in, but either I do not understand fully or assume too much (more likely).
 

1. Comment - Opening the Synth Property page after insert shows "Enable MIDI output" as disabled, yet the drop down on the synth rack has this checked (there is a thread already on this one).
2. Question - If inserting another VST similarly, is setting its input to "Geist->Channel X" all that *should* be required?
3. Question - I cannot see the "guts" of enable MIDI output other than via hit-or-miss testing. Is there a recommended way to monitor MIDI events being triggered within SONAR (i.e. MIDI events that are "free game" for any echoed VST to fire on)?
4. Comment - One issue I am facing is that I can op-test this, but results are not consistent... trying to intercept a PAD firing the Geist engine (or using its step sequencer) may very well not fall into the "MIDI output" as it is internally generated (and intended for the Geist engine), yet in some cases this does in fact pass on.
5. Comment - Geist allows firing on 10 channels, but this post by Noel leads me to believe that the "MIDI output" is limited if it is a VST2.

I may be barking up the wrong tree here, but what I would like to do is pad-fire Geist (via the patterns) and have those be exposed by channel for other VSTs to use. What "enable MIDI output" is truly doing, how to monitor what is going on within SONAR, and possible limitations of the guts of Geist are where I am currently wallowing. All three of these seem to be intertwined in some way that it makes getting a grasp on it difficult.
 

I may have inadvertently found my nemesis playing around, but introduces a (possible) caveat of recording vs playback to consider.

1. Pad/Pattern triggers on Geist do, in fact, send MIDI triggers out as free game.
2. Triggers are by engine, no issues, can freely use as inputs to anything else.
3. The kicker thus far - Geist cannot be used to drive itself via this method (will create a "MIDI loopback" if there is such a thing) - input must be to none or an independent source (to take advantage of external triggering).

Number 3 may be what I had inadvertently triggered previously, but need to validate this in SONAR first. The above was tested in S1 v3 (demo) without issues, then the project closed/re-opened several times to "check."
 
Edit: The issue in the submitted CWBRN still stands. Platinum will load/run VSTs without issue (per above) until the point that a project is closed/re-opened (without a restart of SONAR or even possible reboot). Platinum has a consistent CTD each and every time a project with this routing is opened/played/closed/re-opened. Something in the "Close" and "Open" cycle in Platinum is triggering "something."
 

I made the mistake running X3 18 months ago, thinking that all synths that exposed midi out also used it for something, at least echo midi input through. This was not the case, I found nothing but arpeggiators that did that.
 
So the lifesaver for me became http://ddmf.eu Metaplugin.
- it allows to load and range of synths and VST midi plugins in a very felxible way
- and it allows to see to that midi in is routed to midi out, so you can serialize a couple of synths on Sonar tracks if you want - one track taking input from another tracks output.
 
So Metaplugin exist as effect(Metaplugin) and synth(MetapluginSynth) to use in many scenarios you have.
 
So the VST instruments I use, I made presets for just loading it inside Metaplugin, and routing midi in to midi out - so that basic functionality is there if I want it.
 

Thank you for the response. Everything is working as expected with the exception of the close/open issue.

Another thing I need to add to the Problem Report came to light. On these CTDs the MIDI in/out status in Win7 remains open and cannot be closed. I always assumed this was a SONAR element but seems it is actually Win7's. Is almost like it is not "released" during that close/open cycle to be reinitialized from scratch. Since that icon is buried out of sight, I didn't notice it until a couple hours later this time.

This looks like it was resolved with the Dorchester update. I installed the update after Noel's post linked in the OP and cannot get Platinum to CTD even with the most oddball routings I can think of.