You can always copy the automation for your volume fader to your aux send fader. It will be the same as sending to aux with post-fader, but with the option to pre-aux the desired insert. Hope that helps.
I’m no programmer, but if inserts and sends could be put into some sort of chain, then the order for things to be done could be changed at will. However, the question is whether or not it would be of any use to other people.
DG
Well all that is made easier si good for workflow. So, if inserts and sends could be put into some sort of chain, it would be welcomed by most of us. 
Couldn’t RME’s Totalmix route the way you want it?
Hi Daryl,
maybe this is what you’re looking for:
→ Senderella by Subminimal - Audio Routing Plugin VST
It’s from 2004 and remained in beta-phase, obviously, but I remember that I used this plugin on several occasions before Nuendo got sidechains.
Kind regards,
I’d forgotten about that plug. I’m sure I used it as well, back in the dark Ages. I’ll look into it. Ta.
DG
Did you ever find a solution to this issue?
The solution was posted by Rucareanu in 2012 but the OP didn’t want to use it.
It consisted of using Inserts 7 or 8 and using PreFader Sends.
This ↓
Reaper has it…again 
There you can choose between Pre-FX, Pre-Fader or Post-Fader
Hi Carvin, correct me if I am wrong but I think from memory that Reaper’s pre-send routing is also pre-fade (like a direct out on some analogue consoles). The OP needed a send that was post-fade but pre-insert (source signal sent to SPAT without the channel inserts). The other limitation for the OP with using a Direct Out is that there is also no gain control over the direct out like you get with a send.
One solution would be to use no inserts on the instrument channel, but use two send/returns - 1 return for the inserts and one (communal) return for SPAT. Hide the original instrument channel to remove it from view / controllers and you have the result the OP was looking for. You could do this in Nuendo as well. It would be a bit of a learning curve to efficiently manage views if you need to ride the send levels to the SPAT strip, but anyone who has mixed sessions with large track-counts will be well-used to show/hide channels so that would not be a real impediment. FWIW.
\m/
This is how it is in Reaper:
Pre-FX is before the Inserts (basically splits the input).
–Insert Here–
Pre-Fader is after the Insert, before fader (like Nuendo’s Pre-send).
–Fader Here–
Post-Fader is after the Fader (like Nuendo’s Post-send).
Yeah - logical (and ubiquitous I think) - pre-insert will be pre-fade.
Of corse, but the question was to have the send prior to the inserts. Hence Reapers Pre-FX (pre Inserts).
Nuendo have only pre-fader and post-fader. NOT pre Inserts (only after).