What you have explained above is that this is not the case. If there are voices used in a song from a sample library, I will alway have to perform the incremental step of loading the sample library based voices into the Motif itself from the USB drive first. I am assuming that this means that there is absolutely no way for the VST to send the actual sound behind the voices/voice elements into the Motif XS? Somehow, the USB stick can load these samples into the DIMM but Cubase through the firewire cannot transfer into the DIMM, although both start with an .X0A file?

I believe in no absolutes, but you are essentially correct! You own a product that works with volatile DIMMs for your samples. So it is always going to be true that you must power up your synthesizer and restore prior to playing it or using it. Therefore, always, you need to have any RAM Samples reloaded into memory. The only way that happens is via the LOAD procedure from a drive (USB stick connected to the TO DEVICE port, or via Ethernet)

When you own an XS w/DIMMs you can have an "Auto Load" that will return your particular Library to playable status.

Understand that IMPORT MOTIF XS SONG does just this: It imports all data recorded to the Tracks of the Integrated Sampling Sequencer. The vocals you recorded are sampled audio controlled by MIDI data. They get imported from the .X0A file and the MIDI note data determines where they are positioned.

These are different from the Voices (instruments) you loaded to the internal USER and USER DRUM Banks of the XS. These are not audio recorded to the sequencer, per se. They are instruments you used to play the MIDI notes. Now had you RESAMPLED these tracks, as audio, to the ISS, that performance would then be documented as audio and it would have been loaded (Imported) in a similar fashion to your three vocal tracks. But you didn't. You are playing them from the XS tone engine.

Solutions exist
The reason I mentioned the XF in the previous post was to make clear, the difference between (old style) DIMMs and the Flash solution, is your Wave Library is always there when you power on. With DIMMs you have to always load on power up. You do have that extra step! Same as an XF owner would if the samples for their Voices was in the XF's volatile SDRAM.

Absolutely... There is a way...
RESAMPLING those tracks containing volatile audio waveforms
RESAMPLING is the process of rendering the data you recorded to tracks of the sequencer as an audio stem.
Isolate the track in question by muting all others
Setup the ISS for Record Type = RESAMPLE
As you playback the track it will be documented, as audio, to the ISS on the track you designate.
If you use "sample+note" it will playback as audio synchronized to your other tracks.
You can then clear the original MIDI performance of that data and use the audio instead.

Now it can be Stored, Saved, and Exported (Imported to Cubase) in a similar fashion to the way you did your vocal tracks... Using the IMPORT MOTIF XS SONG.

RESAMPLING those user Wave dependent Voices (before Importing) can ensure all your data is in Cubase.

The "V" in VST is virtual. Thinking the VST would take care of the a Drum Kit samples... Well, no. No more than it could take care of the samples used in the Full Concert Grand (Preset 001). I always use analogies... The instruments you played are not on the tracks of the sequencer. Only the performance you played with those instruments is documented. In the real world: you record a guitarist's performance, the notes sounded. You do not transfer the guitar itself to the recorder. Make sense?

Your vocals are imported! not the singer! 🙂

Cubase can look in a .X0A file, but for the reasons I mentioned, will not transfer the sampled data that is used to create an instrument to your DIMMs. The parameters of your mixing setup and all the Voice parameters - EXCEPT the oscillator - are restored rather rapidly via BULK (a type of MIDI transfer). You do not want to go back to the early 1990's when samples that constructed the instruments themselves were bulked ... It literally took forever in today's terms. SY85 and TG500 could bulk samples ... Yikes! Back then we were not talking about the 100's of MB or a GB of samples either (not even close) and it still took forever. MIDI bulk is not any way to let friends transfer data the size of today's audio samples, trust me!!! The VSTi is only routing, the XS as a VST still uses the dedicated hardware of your Motif XS. Therefore it follows the samples of your Voices must be loaded to the hardware. And as stated this must be via either USB Load or Ethernet Load

Elegant solution
The Motif XF. Where you extend the available Wave ROM with Flash Boards. Simply: the Voice's Samples are always accessible on power up. You would have installed the samples that construct the "YAMAHA Oak Kit", the "Tp Bright" the "Bari Sweet", and the sampled Elements of the "Natural Aah Choir" to your Flash Board... Extending the resident WAVE ROM. Now any time you have a composition that requires these waves they are ready and as accessible as the preset waves.

With an XS you have 355MB of permanent Preset WAVE ROM
You extend the WAVE ROM with up to a GB of volatile RAM

With the XF you have 741MB of permanent Preset WAVE ROM
You can extend the set of always available Wave ROM by Flash Boards.
Of course, if this is not feasible, RESAMPLING can offer a viable solution depending on the length of your composition and the size of your DIMMs.

Anyway, hope this has been helpful. Your workflow would be the following:

Power up your XS connected to a USB stick that returns (Auto Load) your Wave data.
Power up your computer and launch Cubase.
When both are powered up and ready... Launch your Project
The AUTO SYNC SETTINGS will restore your Voice parameters and Mixing setup.
Play!

Enjoy!

Extra Credit
Description of the Cubase Import Song function is found in the "Extensions for Steinberg DAW Owner's Manual (for Motif XS)".

I apologize that this is a few days later than I meant to but I just wanted to thank you for your guidance and help in the last weeks helping to solve the above challenges. Your last explanation helped perfectly to fill in the remaining blanks for me. I've tried the final workflow you recommended and it works well and quite honestly doesn't even take a lot of time anymore given the much cleaner and shorter .X0A file I am using. In summary, you have helped resolved the time-out issue during synchronization (the issue was some illogical info in my way too big .X0A file), helped understand why two audio tracks showed up as midi and how to fix that (make sure PC command transfers either during moving a pattern chain to a linear song, or add it back later manually), and helped me understand how to handle sample library-based waveforms (always load them from a USB stick first to the Motif XS) when working with Cubase. All problems solved! Thank your for this fantastic support!

Regarding the XF... I would love to have the flexibility it offers over the XS but I may wait it out and make an upgrade decision when the XF's successor comes out... looking at historical MOTIF product releases, we could be perhaps 1-2 years out max (I know you cannot give a hint on this and by no means am I trying to get one)... so will wait with a lot of excitement and see what comes out next.

Thanks again for the phenomenal user support over the many-many years Bad Mister!